Windows 7 loses its drive letters and I have to keep manually assigning a drive letter everytime I plug in a hard drive, whether it's internal or external.

The only way to get around it is to reinstall Windows 7 but the problem will come back after a few months. We are a PC repair company and plug in many drives during the say and it can be very frustrating having to keep assigning a drive letter every time a drive is plugged in. Windows Updates are turned off so it can't be that.

Any reason why this would have happened?


I think it probably had to do with the windows saving different drive letters for different drives into its registry. The registry keys are: HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices

I guess if you delete the unused entries it may help... but you may as well ruin the system and need a reinstall if you somehow messed up with it..

so there you go...

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  • Thanks for that. Do you know how to find out what the volume id of the current drives installed are so that I do not remove the wrong ones? img.ly/images/629138/full – Dean Perry Dec 17 '10 at 12:03
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    c:\> mountvol [enter] – bubu Dec 17 '10 at 12:08
  • may i stress once more that it is very dangerous stuff to edit. remember to at least make a restore point/backup beforehand – bubu Dec 17 '10 at 12:09
  • OK thanks. Just doing an image before I change anything – Dean Perry Dec 17 '10 at 12:18
  • Also read @harrymc's link.. it's a good read – bubu Dec 17 '10 at 12:28

It may be that since you are plugging-in so many disks, Windows runs out of drive letters.

When that happens, you can assign the drive letter manually from Computer Management / Disk Management.

If you would like to make Windows forget all drive letter assignments, read this carefully:
Change or Delete System Drive Letter via Registry to Remove Conflict.

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I'm using CCleaner to keep my registry all nice and tidy, and as a result, it seems to be wiping the drive letter assignment registry items. While this isn't a solution per se, it seems to me that you may be running into something similar since you're a repair shop and may be trying to keep your test systems squeaky with a daily scheduled registry sweep which could be causing the issue.

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From Microsoft forum:

DOS run diskpart. Sure enough, the volume was perfectly ok, but the "hidden" attribute was set. So a quick




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  • Please add a link to the source. – Christian Oct 31 '13 at 16:19

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