Clean Installing Windows on the EP121

Update: The direct driver links below no longer work.  To obtain the drivers discussed in this post, please refer to the link information here:

Original Post:

I took the plunge and decided to completely wipe my EP121 and install a clean retail version of Windows 7 Ultimate on it.  There are typically two reasons to do something like this:

1) Improving overall system performance

2) Reclaiming disk space

In the case of the EP121, I’ve found that clean installing Windows did not improve boot times or resume times and I noticed no difference in overall system performance.  I also found that simply un-installing the applications I wasn’t interested in was just as efficient in reclaiming disk space.  Further – clean wiping the machine will force you to search through the recovery disks for software you do want to re-install – like ArtRage.

So bottom line – clean installing the EP121 for performance gains or reclaiming disk space is not necessary.  That being said, if you want to go through the process, here are the steps I followed:

Prepare Drivers

There are 2 drivers that you will need to prepare ahead of time to make the process go smoothly.  The first is the WiFi driver.  Although this driver is on Windows Update, it is not on the retail Windows media disc because the WiFi part did not exist back when Windows 7 was released.  So if you don’t have this driver, you will find yourself in a catch-22 situation since you will have no way to connect to the network to access Windows Update.  You can download the WiFi driver from here:

You will need to navigate to the Wireless section as shown here:

The second driver is the Intel HD Graphics driver.  It doesn’t necessarily need to be downloaded before clean installing but it’s very convenient to do so since the driver on Windows Update is older than the driver on Intel’s website and the older driver doesn’t perform as well as the latest driver.  So to keep your system performing well, you’ll want to download the driver from Intel’s website located here:

32-bit driver:

64-bit driver:

Make sure you copy these drivers to a USB storage device or SD memory card as you will be wiping your EP121 drive clean.

Installing Windows

Now it’s time to start the installation.  You will need a wired USB keyboard (mouse is optional).  If you decide you want to use both a keyboard and a mouse, you will need to use a USB hub since one of the 2 available USB ports will be occupied by an optical drive loaded with the retail Windows 7 DVD or a bootable USB drive with Windows 7 (available for purchase/download from Microsoft’s online store).

Connect the keyboard and Windows 7 retail media to the EP121’s USB ports.  Connect AC power.  Turn on the machine and hold down the ESC key to bring up the boot menu.  The menu will look something like this:

The P1: SanDisk SSD P4 is the internal EP121 SSD device.  The other item listed will be the boot media you connected (in my case it was a Sony device).  Select the boot media and hit Enter.  (Note: the latest BIOS for the EP121 will automatically boot from any bootable device it finds connected to USB – so it may not be necessary to bring up the boot menu at all depending on which version of the BIOS you have installed.  The latest BIOS is available on Asus’ download site).

The Windows installation will now begin and you will be prompted to choose your language settings.  Once that’s done, Windows will present an option to select the type of installation you want.  Since we are performing a clean installation, you will want to choose the Custom (advanced) option like this:

Next you will be asked where you would like to install Windows.  You will need to select Disk 0 Partition 2:

Windows setup will now proceed to install files on the EP121:

After about 12 minutes or so, Windows Setup will complete the installation and state that the system will be rebooting.  At this point, you must disconnect the Windows 7 boot media or the system may boot again from the USB media and restart the installation from the beginning.

Upon reboot, you will be prompted to enter the Windows 7 product key.  If you are installing Windows 7 Home Premium 64-bit, you can use the product key located under the EP121 bluetooth keyboard.  If you are installing a different version of Windows, you will need the appropriate key.

Setup will continue and ultimately leave you at the default Windows desktop.  You can now attach the storage media you used to hold the WiFi and graphics drivers that were previously downloaded.  Proceed to install both drivers by running their respective setup executables.  (note: the WiFi driver also installs the bluetooth drivers).

Windows Update

Once the WiFi driver is installed, you will be prompted to reboot at which point you can join a wireless network and proceed to Windows Update (Start -> All Programs -> Windows Update).  You will see quite a few updates listed.  If you select the Optional Tab, you will see all the device drivers listed:

If you are installing Windows 7 Ultimate, you will also see about 34 updates related to languages that can be installed.  Go through the list selecting the updates you want to install making sure you select all the device driver updates – these are important.  You may see an update related to the touch firmware.  This update will flash the touch controller so you must be careful not to touch the display while the touch controller is being flashed.  Once the updates are applied, you will be prompted to reboot the system.  Depending on which driver updates were applied, you may discover that Pen and Touch are no longer functional.  If that is the case, you will need to attach a keyboard or mouse so that Restart can be selected.  After the system reboots, Pen and Touch will be functional again and you will be prompted with a window asking if you want to enable the Asus G Sensor.

The G Sensor is the device that detects when the slate is in motion and enables automatic screen rotation.  So you will likely want to enable the sensor.

Go back to Windows Update and apply any remaining updates that you want.  Repeat this process until you’ve exhausted the list of updates you want to apply.  (Note: Some updates won’t appear until other updates are applied which is why you need to keep going back to check).  At this point there should be no unknown devices listed in Device Manager:

Once you’ve confirmed that there are no unknown devices and that you have applied all the updates you want, you can proceed to run Winsat by going into Control Panel and selecting “Performance Information and Tools”.  Winsat will perform some system tests, enable Aero graphics (desktop transparency effects) if they aren’t enabled and present you with a system rating like this:

Cleaning Up

If you made it this far, congratulations, Windows 7 has now been cleanly installed on your EP121.  There is one final step which involves cleaning up your storage drive to remove any of the restore points and temporary files left behind during this installation process.  To do this, tap on Start -> All Programs -> Accessories -> System Tools -> Disk Cleanup.  Select the “More Options” tab and tap the lower “Clean Up” button in the “System Restore and Shadow Copies” section:

Once the clean up is done, tap OK and confirm the deletion of the remaining unnecessary/temporary files.  That’s it – you’re done!

Wrap up

Looking at the disk usage, we see that on a 64GB SSD system there is 41.5GB free space remaining out of a total 59.5GB.

So Windows 7 Ultimate 64-bit took up 18GB of storage.  (other versions of Windows 7 (i.e. Home Premium) will likely occupy less space).

In terms of boot time, the system took 28 seconds to boot, connect to WiFi and load a webpage.  This is exactly the same amount of time it took with the factory pre-loaded version of Windows 7.  You can see a video of that in my Product Tour post located here:

Resuming from sleep mode took 3 seconds from pressing the power button to re-establishing a WiFi connection:

One final piece of advice: if you installed Windows 7 Ultimate, you can create a system image backup onto an external USB drive or network location.  I would recommend doing this as you would then have a clean image that you can re-apply to the system with ease should the need ever arise.

Have fun…


42 Responses to “Clean Installing Windows on the EP121”

  1. I’m not sure where you’re getting your information, but good topic.
    I needs to spend some time learning much more
    or understanding more. Thanks for magnificent info I was looking for this information for my mission.

  2. So i just need the bios, wireless, and graphic in the usb? Do i need the window 7 cd?

    • You need to have a retail version of Windows 7 on some form of media in order to do a clean install. This means you either need it on DVD (so you must connect an optical drive to the machine) or you will need it on a bootable USB drive (which you can prepare online from a utility on Microsoft’s online store).

  3. To those people who are having trouble with G sensor not working, make sure to uninstall the driver in device manager and ALSO the G sensor program listed under control panel (uninstall programs). Then reinstall the Asus G sensor driver from the Asus website. This seemed to work for me after many failed attempts of just reinstalling the driver.

  4. Paul Gibbs Says:

    I have also tried a reinstall on this machine. I can get it to recognise the external drive but it won’t start the operating install. tried this with the ASUS restore and Windows 7 disc. Any suggestions… Thanks

  5. I have had an ep121 for about 7 months now, and i’m sad to say it is sort of dying. For the first few months I had it it didn’t glitch and I had no problems. Then it started to freeze up on me constantly, the graphics stopped working for a day, the whole system slowed down, and it would randomly shutdown. I have even had a situation were the tablet had 90% percent battery and it would refuse to turn on or shutdown. So I think I am going to restore it as best I can and sell it for $900.

  6. Thanks a lot….


  7. I tried to do the clean install as written when I select custom I only show 1 partition no second one to select what am I doing wrong?

  8. Anonymous Says:

    to get the screen to flip, reinstall the g-sensor driver and update windows

  9. Anonymous Says:

    So far I’ve been able to reinstall everything just fine. I reinstalled the G sensor driver but now my screen flashes but doesn’t rotate. Please help!!

  10. Has any one figured out how to get the preinstalled software back after a clean install of windows 7

  11. Just used this advice to upgrade to Ultimate so I can join my network at work. Great walk-through! One bit of advice, remember on the newer BIOS that any USB left in during reboot will automatically default to that device for booting. Pulling it out at the first reboot during windows installation will save some confusion!

  12. Anonymous Says:

    I read the previous post and just need a little clarification. My medical record software for a physicians office runs Windows 7 32 bit only. Can that be installed on the Asus 121?? What is the procedure if it is compatable?

    • Anonymous Says:

      Ya 64-bit computers can run 32-bit software. I have an asus ep121 and I have tons of 32-bit software on it and it runs fine.

  13. Anonymous Says:

    Hey, does anybody know if and when there will be a sady bridge version of the ep121? Thx!

  14. I see this thread has been quiet for a while. are you still using the EP121 if so what are your thoughts at this time. Also what would be the main reason to go from windows Home Premium to Windows Ultimate.

  15. c. merriman Says:

    Thanks – this is just what I have been looking for – I was debating on buying the EP121 or waiting for the B121 which is suppose to be aimed at “Business” with Windows 7 Pro.

    re there any functions that don not work with the upgrade?

  16. Great post and very helpful.

    I just did a clean install on my machine.
    1st pass was 7 Ultimate but I didn’t have/spend the time to install all the extra drivers like button controls, etc.
    So I reverted to the base Asus build and Anytime Upgraded to Ultimate.

    After upgrading, my Bluetooth devices wouldn’t reattach after rebooting.
    Fixed this by rerunning the Asus wireless driver install.
    Works like a charm now.

  17. A very solid site, thanks for keeping it so easy to understand!

    Now, since it’s a full-fledged PC does that mean I can install XP? And if not from scratch I assume it is still do-able by dual-booting a copy of it but just want to see if that step ins’t needed.

    Thanks for a great site, I look forward to the answer!

    • You can install XP but for the digitizer to work – you may also need to use XP Tablet PC Edition which is not available generally to end users. It was only available as a pre-installed option on a new PC.

  18. Thank you for posting this info. You saved me a lot of time! greatfull

  19. Hermann Says:

    Do you remember the memory usage after booting? Either Windows 7 64-bit is a huge memory hog or the extra software from ASUS is responsible for it. The factory install uses 1.7GB of RAM without having any applications launched. Do you know which ASUS services I can disable to improve memory usage? Do you have the 32-bit or 64-bit version installed?

    • I am using the factory installed OS image which is Windows 7 Home Premium 64 bit. I un-installed Asus Webstorage, Asus Vibe and Roxio Player Deluxe.
      I don’t have my machine handy at the moment to check memory usage but my performance has been great so no complaints on my end.

    • Hermann Says:

      Do you know what these ASUS utilities actually do and which ASUS utilities are required for the EP121 to work and which are just nice to have? E.g. what is Hotkey or ATK for?

    • Hotkey and ATK are required to make the buttons work. You need to keep those. But Asus Vibe and Asus WebStorage are not necessary.

    • Hermann Says:

      Thanks for the quick reply. Do you also know what APRP and Media Sharing are for? Do you think the Memory Clean utility actually helps?

    • Unfortunately I’m not familiar with those.

    • I’ve installed the 32bit version of Windows 7 Professional today and I am glad I did. Disc and RAM usage without drivers and Windows Update was as follows:

      Disc: 11GB
      RAM: 500MB

      After installing all the necessary drivers, necessary utilities, Windows Updates (incl. Service Pack 1), the usage is as follows:

      Disc 14.8GB
      RAM: 625MB.

      This is a huge improvement from 18GB disc and 1.7GB RAM usage. The folder structure also looks much cleaner because you only need the x86 files. I also noticed it performs much better.

      I also found out that APRP stands for Asus Product Registration Program, which is obviously not necessary. The media sharing utility allows you to share media (duh!), so just a nice to have.

    • And another improvement I forgot to mention. Number of running processes went from about 90 to only 56. A few things I found annoying on the default installation are also gone, so I definitely recommend a fresh install. Thanks again for your guide, it was very helpful!

  20. I am in process of loading Win7 Ultimate 32bit, because Office 2010 is 32 bit, and I have international language pack to ink and proof with. My understanding is that all have to be 32bit system or 64bit system in order to work together. Does anyone know if that’s correct?
    With default system/office 2010 32bit and language pack, OneNote could not convert ink to text in any other language but English. Hoping I’m not wasting my time going to 32bit and find out that other things don’t work – also can you post the default icon and taskbar settings for the icons or is one of the downloads from Asus able to set the theme?

    • Office 2010 32 bit will work on Win7 64-bit. As far as languages – I’m not aware of any issues with the language packs that are installed on ultimate.

  21. Good Work!
    Thank you. I have the same question with honeycomb, and how we can install; if you know anything about that…

  22. Says:

    Please, at any given time, I have about 89~90 processes running on my Ep122 slate & I`m sure this is affecting battery usage as I only struggle to get 21/2hrs even with aero turned off as well as bluetooth. Could you give an insight into how many would be the optimum number to allow & what processes you`d disable on your slate without endagering essential ones. I understand it depends on one`s usage,still your perspective would be helpful. Thanks & great work.

  23. Excellent. Thanks for that. I guess if I were to do the clean install thing I’d start by making a stripped down Windows 7 installer disk using vlite or 7customizer.

  24. It looks like you clean-installed the 64 bit? Do you have insights on the merits or dangers of upgrading to the 32-bit 7pro version of the OS? Am concerned about legacy programs not running properly on a 64-bit system. Does anyone know why this tablet is running 64-bit? It seems like an unusual choice.

    • The drivers and Asus services (like hotkeys) were developed and tested for 64 bit. So although they will likely work with 32 bit, all the testing was done on 64 bit which is why I clean installed the 64 bit OS. All legacy software (Win 32 based API applications) should have no problem working on 64 bit – I use 64 bit on almost all my machines and have never encountered a compatibility issue with legacy software. One example of the advantage for 64 bit comes with 4GB+ RAM systems using apps like Photoshop that can make use and take advantage of the larger address space. They will generally perform faster. Also note that if you have 4GB RAM installed on the EP121 and installed the 32 bit version of Windows, you would not have access to all 4GB of memory. You can only access all 4GB RAM with the 64 bit version of Windows.

  25. Thanks for your articles about EP121.

    After re-installing Windows 7 Ultimate, the cpu score of my Ep121 shows 3.0 or 3.1. Do you have any thought about this? In addition, I feel the systems is slower than before….,

    • This was a known problem with the older BIOS. Asus has posted BIOS 4.01 on their website which will fix the low CPU score issue.

  26. You can run Android on it:

    But why would you cripple this awesome machine?

  27. Do you think i could run device as multi-os, with booting options at the beginning to chose linux. Also do you think android honeycomb could be installed in this deveice?

    • It’s a PC – so it can be configured to boot multiple OS’s like any PC can. As for honeycomb, I don’t have any experience with it so can’t really comment.

  28. Very nice job with all the steps. I certainly appreciate the effort, and look forward to my unit when delivered. Again, thank you for delivering confidence this can really be used as a computer (not just a *pad).

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