To keep Windows XP from deleting restore points of the volume in Windows Vista, add the following registry entry under the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline registry subkey in Windows XP:
Value name: \DosDevices\D:
Type: REG_DWORD
Value data: 1
Note If the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline registry subkey does not exist, you must manually create this registry subkey. Create this registry entry when you have installed Windows Vista on the "D" partition in Windows XP.
Effects of this workaround
After you restart Windows XP, you cannot access the volume that is created in Windows Vista from Windows XP. However, you can still access the volume that is created in Windows XP from Windows Vista. You must use Windows XP drive or an additional drive such as a USB thumb drive for data exchange.
Limitations of this workaround
This workaround only protects the volume in Windows Vista from being accessed or changed by Windows XP. If you have more volumes or if you want to add a volume from Windows XP to the system restore settings in Windows Vista, the system restore (Volume-Shadow-Data) on those volumes will be still overwritten. To avoid this problem, you must add those volumes to the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline subkey. If you add the Windows XP volume to that subkey or if you delete this volume drive letter, you cannot then start Windows XP.
You can use this workaround only when the restore points for Windows XP and for Windows Vista are mutually exclusive. The restore points are mutual exclusive when no restore points are common across the volume in Windows XP or the volume in Windows Vista. For example, consider the following scenario:• The C driver is a volume in Windows XP.
• The D driver is a volume in Windows Vista.
In this scenario, the Windows Vista restore points are added on the E driver. Then, you must change the registry entry of the E driver under the HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\Offline" registry subkey to 1.
Also, a common volume can be used for data exchange between Windows XP and Windows Vista. However, restore points must not be defined on this common volume.
For more info see:
http://support.microsoft.com/kb/926185/en-us
