Drive Letter assignments in registry


Jan 19, 2011
When I change drive letter assignments with Microsoft's Disk Management accessory, normally they remain as I assigned them once I reboot, but this is no longer happening. XP has its own idea of what devices it wants to belong to which drive letters, and every time I reboot, it's undoing my new assignments.

Is there a way for me to change the assignments directly with regedit? Maybe then they will stick.

Possibly related is that I am now getting a "Windows has installed new hardware message" asking me to reboot for the changes to take effect. This message is coming up every time I reboot, whether I have changed drive letter assignments or not, and I don't know how to make that go away.

Note: The new hardware in question, whatever Windows seems to think it is (none has been added), is not assigned to any of the letters that have been changed. The system has already been checked for malware, in case you suspect that. It would take too long to explain how I got into this mess.

Thanks for any assistance.


Aug 29, 2011
To start, change the drive letters in the Disk Manager, obviously except for the C:\ system drive, next go to Control Panel \ System \ System Restore tab \ select the all supervised drives one by one starting with the D drive, click on Settings \ slide the marker all the way to minimum and mark the box in Disable System Restore on this drive. Accept and do the same on the next partition... next close all applications and don't use any of the drives you changed letters on, before restarting the computer.

Next go to Start \ Run \ and type: "regedit" (no quotes) and hit Enter... next Go to HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices and delete all the REG_BINARY values on the right pane of the MountedDevices registry Key... and immediately restart the computer. It's perfectly safe to delete all the Mounted Devices values, I have done this many times and never experienced a problem. Most of these values are leftover from previous drive letters... for instance; there should be two values for each drive (one starting with \?? and one with \dos ) this is normal... but there will probably be more than two REG values... this is because each time you change a drive letter, the values that represent that drive are replaced by two... well, can't remember if only one REG value is replaced but the old values are replaced and not deleted. In your case, my guess is that when you change drive letters, you keep using the drives, this and giving the system enough time, allows it to discard your changes and use the same drive letters as before, so don't use the re-lettered drives again untill you restart the computer.

So close all apps and disable System Restore on non system drives, 2nd change the drive letters, 3rd delete the REG_BINARY values, and 4th step, immediately restart the computer. If the drive letter changes stick as you set them up, re-enable System Restore on the drives you want it to supervise.

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