Configuring Drive Letters

Each primary partition, logical drive, or volume on a disk can have one drive letter and one or more drive paths associated with it. You can assign, change, or remove driver letters and mount points at any time without having to restart the computer. Windows Server 2008 also allows you to change the drive letter associated with CD/DVD-ROM drives. You cannot, however, change or remove the drive letter of a system volume, boot volume, or any volume that contains a paging file. Additionally, on GPT disks, you can assign drive letters only to primary partitions. You cannot assign driver letters to other types of partitions on GPT disks.

After you make a change, the new drive letter or mount point assignment is made automatically as long as the volume or partition is not in use. If the partition or volume is in use, Windows Server 2008 displays a warning. You must exit programs that are using the partition or volume and try again or allow Disk Management to force the change by clicking Yes when prompted.

To add, change, or remove a drive letter, right-click the primary partition, logical drive, or volume in Disk Management, and choose Change Drive Letter And Paths.

Any current drive letter and mount points associated with the selected drive are displayed. You have the following options:

• Add a drive letter: If the primary partition, logical drive, or volume doesn't yet have a drive letter assignment, you can add one by clicking Add. In the Add Drive Letter Or Path dialog box that appears, select the drive letter to use from the drop-down list, and then click OK.
• Change an existing drive letter: If you want to change the drive letter, click Change, select the drive letter to use from the drop-down list, and then click OK. Confirm the action when prompted by clicking Yes.
• Remove a drive letter: If you want to remove the drive letter, click Remove, and then confirm the action when prompted by clicking Yes.

Note: When you change or remove a drive letter, the volume or partition will no longer be accessible using the old drive letter, and this can cause programs using the volume to not work properly or can cause the partition to stop running.

If you installed the operating system on a drive with an odd drive letter, such as F or H, it would seem that you are stuck with it, which might not be for the best if you really want the operating system to be on a different drive letter, such as C. Although Disk Management and DiskPart won't let you change the drive letter of a system volume, boot volume, or any volume that contains a paging file, there are workarounds. For volumes containing paging files, you must first move the paging file to a different volume, and then reboot the computer. You are then able to assign the volume a different drive letter-provided it isn't also a system or boot volume. To change the system or boot volume drive letter, you must edit the Registry using an account that is a member of the Administrators group. Don't do this without creating a full backup of the computer and its system state first.

Start Registry Editor by typing regedit, and then access the HKEY_LOCAL_MACHINE\ SYSTEM\MountedDevices key. This key has value entries for each of the drive letters used on the computer. Find the value entry for the system or boot volume that you want to change. Right-click it, and choose Rename so that you can edit the name. Change the name of the value entry so that it points to the drive letter you want to use. If that drive letter is in use, you must rename two value entries. For example, if you want to rename D as C and C is already in use, you must rename C to an unused drive letter and then rename D as C. Make sure you edit the boot configuration data so the right disk is set for booting the operating system. Afterward, restart the computer.