System restore Points in Vista Keep Disappearing
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Link:

http://support.microsoft.com/kb/926185

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SYMPTOMS
When you use the System Restore feature in Windows Vista, you receive the following message:
No Restore Points have been created on your computer's system disk.
Additionally, only the most recent backup files from Windows Vista Complete PC Backup are available. Earlier versions of the backup files are unavailable. You experience this problem if you are running Windows Vista or Windows Server 2008 on a computer that is also configured to run an earlier Windows operating system.

Note This configuration is known as a dual-boot configuration.
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CAUSE
This problem occurs when you start the computer by using the earlier operating system, such as Microsoft Windows XP or Microsoft Windows Server 2003. In this situation, the earlier operating system deletes all the restore points that were created in Windows Vista. The earlier operating system also deletes all Complete PC Backup files except the most recent version of these backup files.
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WORKAROUND
You can use either of the following methods to work around this problem.
Method 1
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.
Support Status of this workaround
Adding this key can have unwanted side-effects to your installation. For example, applications that put data on this drive before available may fail. If there is a reporting problem reported to Microsoft, you will be asked to delete this value


Method 2
To work around this problem, use the Bitlocker feature on the volume in Windows Vista.

Bitlocker is a built-in security feature in Windows Vista. When Windows Vista starts, the Bitlocker feature should be enabled on the Windows Vista volume on which Windows Vista restore points are enabled. When Windows XP or Windows Server 2003 starts, the Windows Vista volume on which the Bitlocker feature is enabled is inaccessible. Therefore, the Windows Vista restore points are intact.

This workaround works for dual-boot configurations (Windows XP or Windows Server 2003 together with Windows Vista).This workaround requires no changes to Windows XP. Therefore, the volume in Windows Vista is still inaccessible when the system is started in Windows XP or in Windows Server 2003.

Note The Bitlocker feature is available for Windows Vista Enterprise Editions and for Windows Vista Ultimate Editions.
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so if you been backing up check to see if they are there

Regards Ben