To open an elevated command prompt, click the start menu, type "cmd" (without the quotes), then press LEFT CTRL + LEFT SHIFT + ENTER and when UAC prompts you, click "Yes".

Once the elevated command prompt is open, run the following commands one right after the other:

DISM.exe /Online /Cleanup-image /Restorehealth

sfc /scannow

When both commands have run fully, reboot your PC. This should eliminate any other surprise issues that you may have. If you really want to go balls to the wall, before you reboot, also run a third command:

chkdsk /R /F C :

There is no space between the C and the : I just put one in because otherwise it gave me an emoji. Also, since it is your primary OS drive, it will ask you if you want to do this upon reboot. When it does, choose YES.

This will ensure that every stitch of your system is checked out from top to bottom to make sure there's nothing else underlying in the system that may screw with things later.

You can also run the last of those 3 commands on the other drive letters as well. Just be aware though that when running the command on other drives, it WILL make the system unmount the drive before doing the scan, and if the drive is particularly large, it WILL take some time. If you're experiencing any other side issues though, it absolutely will address them.

Right click your Start Menu, then click "Disk Management"

When the list of drives comes up, you'll be able to click on the drive itself (on the left) or the partition, then click "Change Drive Letter and Paths"

You may have to change each drive more than once to do a little magic shuffling of the drive letters, but this is where you absolutely CAN change them back.

If the disk management won't let you use the drive letter because it claims it's already in use, even though it's not, there's a solution for that too.

Click the Start Menu, then type "cmd" (without the quotes) then press the LEFT CTRL + LEFT SHIFT + ENTER

When prompted by UAC, click "Yes"

Then, give the command prompt the following command

mountvol /r

Let the process run, then it should be clear, then reboot your PC.

IF it STILL does NOT want to let you use that drive letter, then you'll need to go in for a bit of a surgical removal, in which case, follow these steps

Click the Start Menu, then type "regedit" (without the quotes) and press ENTER

You'll want to look under HKEY_LOCAL_MACHINE\SYSTEM\MountedDevices\

Look for entries that say \DosDevices\D: (or whatever drive letter(s) it won't release) then right click it and click "Delete"

Once the phantom entries are gone, simply reboot your PC, and you'll be back in business