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Dual booting Windows RT and RT 8.1

OP xsoliman3

28th June 2013, 10:37 PM   |  #1  
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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://forum.xda-developers.com/show....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
Last edited by xsoliman3; 14th July 2013 at 11:56 PM.
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28th June 2013, 10:41 PM   |  #2  
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Note, this is a hack

The correct method would be to set up seperate OS partition on the internal flash drive
(but a bit small to do that)

Or to get the alternate OS to boot from SD card
28th June 2013, 10:51 PM   |  #3  
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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)
Last edited by xsoliman3; 28th June 2013 at 11:09 PM.
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29th June 2013, 07:13 AM   |  #4  
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You can create a VHD and extract recovery WIM there to get a complete copy of OS. Earlier I've played with that with success.
One note: you can't use the recovery to restore the original "main" windows while BCD has an VHD entry - it fails with an undescriptive error.
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29th June 2013, 07:59 AM   |  #5  
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My windows8.1 recovery file is .esd not .wim.So I must install windows8.1 first then make a windows8.0 vhd?And microsoft says windows rt cant boot from VHD.
29th June 2013, 01:54 PM   |  #6  
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Quote:
Originally Posted by windowsrtc

My windows8.1 recovery file is .esd not .wim.So I must install windows8.1 first then make a windows8.0 vhd?And microsoft says windows rt cant boot from VHD.

Yes, just take WIM from the recovery partition of 8.0, extract it to VHD, then upgrade to 8.1
I was playing with the windows PE - it could boot from VHD. So I assume that "big" RT would boot too, but had no mood to finish tests.
Last edited by mamaich; 29th June 2013 at 01:57 PM.
29th June 2013, 06:00 PM   |  #7  
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Enjoy this while you can, because I suspect that the Windows 8.1 final release will include a firmware update that locks out booting 8.0 forever on your device.

Also, disable Windows Update or change it to manual mode, on both 8.0 and 8.1!! I think Microsoft will release RT 8.1 as a free upgrade that is forced upon 8.0 by being labeled an important Windows update.
29th June 2013, 08:35 PM   |  #8  
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I think I am strong enough to return my surface to microsoft and get my money back if microsoft block my windows 8.0.And then I will say goodbye to any windows rt device.
30th June 2013, 04:22 AM   |  #9  
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Quote:
Originally Posted by Myriachan

.. I suspect that the Windows 8.1 final release will include a firmware update that locks out booting 8.0 forever on your device.

Definitely not, at least not immediately after the 8.1 official release. As this would cause lots of complains and support calls from people not being able to use the recovery USB disks in the case if the upgrade process goes wrong or if they'd like to return to backup.
30th June 2013, 04:37 AM   |  #10  
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Quote:
Originally Posted by mamaich

Definitely not, at least not immediately after the 8.1 official release. As this would cause lots of complains and support calls from people not being able to use the recovery USB disks in the case if the upgrade process goes wrong or if they'd like to return to backup.

Microsoft is copying Apple--that is the whole reason Windows 8 exists--and Apple is even worse than this, giving Microsoft plenty of precedent. On iPads, not only can you not downgrade after you upgrade, you can't even do a restore to your current version. If your iOS device is corrupted, you have to upgrade to the newest version.

Apple's enforcement of this mechanism is that during the reflash operation, the boot ROM generates a random challenge that needs to be answered by Apple's servers with public-key cryptography. Therefore, you can never flash a version of the OS to your device unless Apple is authorizing that version at that particular moment.

I don't think that Microsoft will add a phone-home requirement to restores like Apple does, but I think that they will lock out the old version.
Last edited by Myriachan; 30th June 2013 at 04:40 AM. Reason: Wrong word

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