Windows 7 – How to Assign Permanent Drive Letters to USB Hard Drives

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...

If this is just for a single computer (i.e., you're not trying to make it the same drive letter no matter what computer it plugs into) then you can do it using the Windows Disk Management tool.

• Open the run command and type diskmgmt.msc to open the tool.
• Locate your USB drive in the list of devices.
• Right-click the drive and select Change drive letters and paths...
• Click the Change... button.
• Choose a new letter from the dropdown list and press OK.
• Press OK through any warnings it gives about programs not working if you change the letter.

And you're done! From now on, when you plug this USB into this computer, it will attempt to use that drive letter again each time.

Note that this can cause problems if you have assigned two USB drives to the same letter at different times and then plug them both in.

My experience with this has been that Windows will avoid using the reserved drive letter unless it needs it (running out of letters). To be safe, just pick a letter further into the alphabet and it will not attempt to use that one by default. To all the drives I use regularly, I do connect each and assign it a letter.