The primary partition drive letter designation is lost when you use WinRE to repair a GPT volume in Windows Server 2008

On a computer that is running an x64-based edition of Windows Server 2008, you use the Windows Recovery Environment (WinRE) to repair a GUID partition table (GPT) volume on Extensible Firmware Interface (EFI) x64-compatible hardware.

When you do this, WinRE repairs the partition table as expected. Additionally, WinRE maintains the signature of the disk.

However, after you restart the computer, the primary partition drive letter designation is lost. The drive letters are changed. For example, before the repair, the drive letter was C, but after the repair, the drive letter is changed to G.

Additionally, Windows Server 2008 does not start, and you cannot see the desktop. You see only a black or blue screen and a white mouse pointer.

This problem occurs when the primary and backup partition tables are corrupted. The drive letters are mapped by using the unique ID of the volume or of the partition. On the GPT, this ID is the partition GUID that is stored in the partition table. When the primary and backup partition tables are corrupted, and when the partition tables are repaired, new partition GUIDs are created. This condition causes the problem that is mentioned in the "Symptoms" section.

Additionally, this problem may occur if the Windows Server 2008 boot partition drive letter does not match the drive letter that is assigned during the initial installation of Windows Server 2008. Windows Server 2008 maintains a record of the drive letters in a registry-based database, and it reassigns drive letters based on the GUID that is recorded for each volume. If the volume GUID is changed or is duplicated by hard disk drive cloning software, the original drive letter may not be reassigned to the boot volume.

Additionally, this problem may occur if you break a system/boot mirror and then try to start to the old shadow drive when the original primary drive is missing or is inaccessible. The volume GUID for the shadow drive differs from that of the original primary drive and does not have the same drive letter assigned to it.

To resolve this problem, follow these steps.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

1. Restart to WinRE, and then press CTRL+SHIFT+ESC to display Task Manager.
2. Click File, and then click New Task (Run�).
3. Type regedit, and then click OK.
4. Locate the following registry key:
   HKEY_LOCAL_MACHINE\System\MountedDevices
5. Locate the DosDevices drive letter registry values. These values resemble the following value:
   \DosDevices\C:
6. Locate the drive letter that you want to change.
7. Right-click the registry value, and then click Rename.
8. Change the name of the registry value to the original correct drive letter. Do not change the value itself.
   
   Note To do this, you must know how the drive letters have been interchanged.
9. Restart the computer.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base: