Dual booting Windows RT and RT 8.1

Here is a simple method of having both 8.0 and 8.1 on the same device. You'll need a 64Gb device.
I've decided not to play with VHD any more and just added the another partition.

So here is what to do (do everything in a running Windows 8.0, not in a command line mode):
1. manage-bde -protectors -disable c:
2. Shrink your OS partition from disk manager GUI leaving about 20 Gb free space.
3. Create new partition over the free space, format it to NTFS, add a drive letter, say, F:
4. Obtain image.wim from your recovery USB or from a recovery partition and do:
Dism /apply-image /imagefile:full-path-to-your-backup-install.wim /index:1 /ApplyDir:F:\
5. Add the needed entries to boot-menu:
bcdedit /copy {current} /d "Windows RT 8.0 copy”
bcdedit /set {guid} device partition=F:
bcdedit /set {guid} osdevice partition=F:
bcdedit /timeout 5
6. Reboot
Select the second OS - you'll see that it boots, but you'll get an error. This is due to the wrong drive letter assignments. Your backup image "knows" that the first partition has drive letter C:, while now this letter should be assigned to the second one. It is easy to fix this, read this article: http://support.microsoft.com/kb/223188. Just boot to a command line environment, run regedit, select HKEY_USERS, use "load hive" menu to load "\Windows\System32\config\SYSTEM" from the second partition (when asked how to name the key - type any name you like), then rename "\DosDevices\C:" to "\DosDevices\Z:" and "\DosDevices\D:" to "\DosDevices\C:" (they are located in HKEY_USERS\your-loaded-key\MountedDevices). Unload hive, reboot - and everything would be fine.

You'll have two OSes, I'd recommend to upgrade the one located on the first partition to 8.1 and leave the newly created one as 8.0, so later, when you'd decide to stay on 8.1 you'd just would need to delete a second partition and expand the 8.1 over the remaining space.

Usual note: be careful when playing with the partitions and registry. As you can't kill the device even by deleting all the partitions (you can always boot from usb and recover them manually) - the recovery process is rather complex for the ordinary user.

This works great for getting both 8.0 and 8.1 on a device - I managed with a 12.3G partition for 8.1, which for the purpose of playing around with it, is more than enough. (I've got a 32G VivoTab RT, so disk space is already at a bit of a premium...)

Of course, you might need to remove some stuff in order to free up the space for the upgrade - after installing 8.0 into the newly created partition and performing the updates (Windows started downloading them automatically, so the disk space was going to be used for a while anyway...) I ended up with about 2G free - not enough for the 8.1 upgrade. It helps to recover as much space as possible - otherwise, as I ended up with in one of the early tries to run the upgrade, it aborted with a message in the setup log about being out of space.

Workarounds:
* Make a restore USB stick and get rid of the recovery partition if you're on a 32G device. On a 64G device, I suspect it's less of an issue but it's still another 4G to play with for a second partition. Make sure you've got your install.wim file from that partition before getting rid of it - that's where your initial OS comes from and you'll need it for actually making the second copy of the OS.

* Disable the paging file. You can (and should) turn it back on later, but for downloading & installing 8.1, it's not needed and occupies a fair chunk of space - the default configuration has Windows tending to use a paging file equal to the size of memory, so about 2G can be released by turning it off. The instructions are floating around elsewhere in this thread for doing this.

* Uninstall all of the pre-installed applications. You can get these back later through the Windows Store if you want them, and they're all removed or replaced in the upgrade process anyway; this got me about 450M back.

From your Start screen: every app that's there, uninstall it. You should be left with IE, Store, and Desktop. Make sure there aren't any hiding under "All Apps" as well.

Once that's done, open powershell as an administrator and run:
Get-AppXProvisionedPackage -Online | Remove-AppXProvisionedPackage -Online

That command will completely remove all of the apps that came with the system. To verify, check (as an administrator) that C:\Program Files\WindowsApps contains only a directory "Deleted".

* Uninstall Office RT.
Again, this comes back in the upgrade, but removing it frees up about 2.5G of space for the upgrade.

As an administrator:
C:\Program Files\Common Files\Microsoft Shared\OFFICE15\Office Setup Controller\Setup.exe

Uninstall all of the components of Office from there.

* Get rid of the Windows Update cache.
As administrator:
rd /s C:\Windows\SoftwareDistribution

It takes up a fair bit of space itself, the update files aren't necessary any longer (the cache will be nuked by the upgrade anyway).

* Finally, run the Disk Cleanup utility and clear out everything. Theoretically, there shouldn't be much to cleanup here because most of the usage that it pulls up is the Windows Update cache, but it never hurts to get back every bit of space you can.

At the end of that, there should be about 6G of free space available (on a 12G volume): the store won't install 8.1 unless there is at least 3.3G of free space after the download completes, and I found that for it to work, you need closer to 4G free.

Once you've finished the upgrade:
* Run Disk Cleanup again and get rid of the old Windows installation.
* Turn back on your paging file.
* If you want any of the apps that were provided with your system, check the Windows Store under "My Apps". They'll all be in the list.

With everything said and done, on 8.1 for a few days, my 8.1 volume has 3G of space left on it.

Dual booting Windows RT and RT 8.1 (almost)


I was original working on dual booting RT from internal flash and from SD card
by adding extra entries in the bcd store and a ‘copy’ of windows on the SD card

Note it actually still boots from the system partition on the internal flash but tries to boot an alternate Windows installation from \windows on the SD card

http://xdaforums.com/showthread.php?t=2343101


But now moved on to dual booting Windows RT and RT 8.1 (both from internal flash)
and almost have it working


Installing the RT 8.1 Preview saves the old OS in \windows.old\windows
Or rather saves most of it, but not all

So you need to pre-save much of the original \windows elsewhere, using the recovery environment, BEFORE installing 8.1
as certain important bits seem to get stripped out of windows.old

Then use the same technique of adding entries to the bcd store to allow the system to boot from \windows.old\windows

It wont be perfect as it will pick up certain hard coded \windows stuff and also will pick up the wrong \Program Files
but should be just about usable, especially in desktop mode which is the reason for keeping the original OS

It does boot, but doesn’t pick up the Start screen properly, so need further work on that


Could do it properly if we shrank the C: volume and set up a new dedicated volume for the alternate OS


Original RT
Use recovery environment to make a copy of
\windows\system32\*
\windows\system32\config\*
\windows\system32\drivers\*

Would be easier to copy \windows /s but then get a bloated mess due to the WinSxS hardlinks

Install 8.1 Preview

copy the copied data over the top of \windows.old\windows
will be lots of access denied for files already there
but will copy the important missing files
including the registry hives, ntoskrnl.exe, winload.efi [need the old winload.efi as the new one wont accept the signature of the old ntoskrnl etc]

Suspend bitlocker (if in use)
manage-bde -protectors -disable c:

bcdedit /copy {current} /d "Windows RT 8.0 hack”
note the new guid
bcdedit /set {guid} recoveryenabled no
bcdedit /set {guid} path \windows.old\windows\system32\winload.exe
bcdedit /set {guid} systemroot \windows.old\windows

Restart (or shift restart)

Select the Windows RT 8.0 hack

The original RT OS boots but no Start screen
but is running and a dot will follow your finger

Need to modify the windows.old registry and fix up something

To be investigated



Can also test and develop this with Windows 8.1 Intel on a PC
That also doesn’t get the full Start screen on the hacked (barstardised) alternate boot back to 8.0


Also best to rename \windows.old to something else, as \windows.old gets removed after a few days

Also as mentioned in the 8.1 jailbreak thread, RT 8.1 wont run RT 8.0 OS binaries or office binaries
(due to the new and more restrictive signatures needed by RT 8.1)

Yes, ofc. I write a warning in my list (I thought it would be self-explaining). Thank you master.
btw I did it. Got dual-booting JB8.0 and RT8.1. everything works very nice. (Even though i used 2nd Partition for win8.1 with only 14,6GB, because I wanted to Keep my highly modified and customized winRT8.0)

For those who want a shortcut on the Desktop to get to advanced boot Options: download shortcut
Works in both 8.0 and 8.1, if C:\ is root path for each (see my last post)
This way you can set the timeout of your boot-menu to 0 and set the OS you are using mainly as Default. To Switch OS simply use the shortcut, OR: open Charms-bar - Settings - Power - hold SHIFT while clicking on restart
After that: [Could not take a screenshot]