Tuesday, August 4, 2015

Restored the recovery functionality of the Asus T100TA tablet


I finally decided to sell my Asus T100 tablet. That's because it is slow (Atom platform  is slow) and the keyboard was broken. (Read about that here) When I contacts Asus, they told me that they weren't selling the keyboard dock separately. Bastards!

I waited to see if Windows 10 can magically make the tablet experience awesome. But an Atom will always be an Atom. Windows 10 was also too slow for me on it. And I frequently got BSODs.

So it is going out of the house. That is final.

Instead of auctioning, I decided to it to Sofmap. I had no idea how much money I would receive due to the malfunctioning keyboard and the various scratch marks on the body of the tablet, but I wanted to give it a try. If Sofmap wasn’t prepared to offer a reasonable amount of money, I would go back to my regular method: Rakuten Auctions.

First things first though. I needed to load factory defaults of the tablet. I was running Windows 10 on it and I wanted to go back to Windows 8.1 that it originally came with. I tried resetting from the Settings app, and it reset back to Windows 10, and not 8.1 I don't have any recovery media to do a manual recovery either.

There is a recovery partition that was hidden from the user, but Windows 10 couldn't see it. Asus had a tool called BackTracker which I thought could reregister the Recovery Image, but it was not supported in Windows 10. It seemed to work under Windows 8.1 and was listed one of the utilities for the T100 tablet on Asus’ website.

So I downloaded Windows 8.1 Japanese from MSDN and performed a clean install using a USB stick which was created using Rufus. BackTracker still didn't want to run, saying that the it doesn't support my system. The heck with that! The inbuilt Windows Recovery functionality didn't work either. It still could not see the Recovery Image which was stored somewhere in the tablet.

I searched around and finally found a way to register the Recovery Image with the OS. There is a utility that comes with Windows called REAGENTC.exe that can register an existing Recovery Image with the OS. The syntax of that command is as follows.

REAGENTC.EXE /setosimage /path <Path of the Recovery Image> /index 1 /target C:\Windows

But there was one issue. The partition where the Recovery Image is stored was a hidden partition. It could not be seen from Explorer or Disk Management. Thankfully, by using Diskpart command, I was able to make it visible. The following were the commands I used sequentially. Note: The disk and partition indexes could be different for you, so read the information provided by List command for disk and partition. I also recommend that you backup anything important before performing anything like this.

  • Diskpart
  • List disk
  • Select disk 2
  • List partition
  • Select partition 0
  • Assign letter=R
  • Exit

After that, the Recovery Partition was visible from Windows Explorer. Then I open up an elevated command prompt and typed the REAGENTC command, with the path of the Recovery set to R:\RecoveryImage. The contents of that folder were inaccessible, however the total size of the other folders was only a few hundred MB which made me realize the necessary files had to be residing inside the R:\RecoveryImage directory.

So I used the following command.

REAGENTC.EXE /setosimage /path R:\RecoveryImage /index 1 /target C:\Windows

It worked and I could restore the factory image from the Settings app. I tried it several times to make sure everything was working correctly. Finally!!!!

Now it is the time for me to get rid of the tablet.

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