[Windows RT General] Osprey00:
OK, I'll give it a shot...

Instructions for installing Windows RT 8.1 RTM on the Surface RT

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1. Ideally, obtain the RT 8.1 RTM ISO that has the Surface RT drivers built in (google "DRIVERS FOR SURFACE RT ONLY___MICROSOFT WINDOWS RT 8 1 WITH OFFICE 2013 RT RTM WOA ENGLISH DVD-WZT"). If the ISO that you have comes with a driver zip file and the ADK installer, then you have the original ISO and will need to manually add the drivers to the ISO before you install 8.1 (or else you might brick your tablet). Do that by first installing the ADK (just the 40MB deployment part is necessary) and then following derausgewanderte's instructions. After you do that, you can continue with these instructions. Warning: Either way (i.e. with either ISO), the drivers are only for the Microsoft Surface RT (not the Surface 2 and not RT tablets from other manufacturers), and you might brick your device if you install on anything else.

2. Optional (but recommended): Make a USB recovery drive in case something goes wrong with the installation or you ever want or need to revert back to 8.0. Get at least a 4GB USB flash drive, insert it, bring up the charms bar, Search under Settings for "recovery," tap the one that's just called "Recovery," click on "Create a recovery drive," choose Yes at the User Account Control prompt, leave the check mark in the box and continue with the wizard.

3. Obtain the product key that your Windows RT is activated with. This is very important because you will not be able to re-activate after installation without it. Follow these instructions to obtain it. To be safe, check that the key is valid by running a key checker, such as The Ultimate PID Checker. Save the key somewhere other than on your tablet.

4. Choose to either create a bootable USB drive (4a) or extract the files and run Setup.exe from the Surface (4b)...

4a. Use Rufus to create a bootable USB drive from the ISO. Ensure that an MBR partition scheme and FAT32 are selected; then, select "ISO Image" from the "Create a bootable disk using" drop-down menu, click the button next to it and select your ISO.

...or...

4b. Extract the files from the ISO, using 7zip (what I used), WinRAR or your favorite ISO viewer; then, copy them to the Surface (or put them on a USB drive or SD card that you insert into the Surface).​

5. If you made a bootable USB drive per Step 4a, shut down the Surface and insert the USB drive; then, hold the Volume Down button while powering on. If you extracted the ISO per Step 4b, run Setup.exe from within Windows RT.

6. When asked, input one of the keys that came with the ISO (see the text file that came with it or the release's description). I used the "CoreARM" one.

7. When asked which files and settings you want to keep, choose whatever suits you. I chose to keep all files and settings (i.e. an upgrade) and have had no issues. The files, settings and apps that I had were all preserved. Other users have chosen to keep nothing (i.e. a clean installation) and have reported that that works fine, too.

* During installation, progress may stall at 0% for a long while. This is common. Don't panic. Just let it sit and it should get going after 20 minutes, at most.

8. After installation is complete and 8.1 is booted up, open the charms bar, tap Settings, then "PC Info" (or go to the Desktop, long-press on the new Start button on the taskbar and select System), scroll down to the bottom of the window, click on the link to Activate and, when asked, enter the product key that you obtained in Step #4.

9. Open the charms bar, choose Settings, "Change PC settings," then "Update and recovery." Check for and install the Windows updates that are available, then reboot. One of the updates is a missing driver. We aren't sure what it's for, but it's best to install the update and reboot before using 8.1 too much, lest you run into something not working.

10. Verify that all of the settings and personal files that you wanted kept were successfully migrated to the new installation. If they weren't or if you chose to "Keep Nothing" during installation, you may find them in the "Windows.old" folder on your C: drive. When you're satisfied that you no longer need anything in the Windows.old folder, you may delete it and reclaim the 2GB or so that it's taking up.

---------- Post added at 12:58 PM ---------- Previous post was at 12:54 PM ----------

That's the Windows Assessment and Deployment Kit, the software tool that you use to add the drivers into the ISO. You some instructions for doing that here, but it's easier to just get the other ISO that's floating around, the one with the drivers already added to it (see Step #1 above for the string to google).

I did notice that with Mail (I don't have any photos or Skype set up yet), but it's live for me now. I may have just needed to wait until I got a new e-mail in 8.1 for it to go live. Try sending yourself a test e-mail. I'm not sure about Photos -- maybe try adding a new photo to your device.