"Sometimes you have to look at things from a cost factor and from a time spent on the project factor. "
Really --- duhhh!!
So your cost factor is to REINSTALL YOUR OS!! Vs making sure the drive letter assigned to a specific device is not already used by some other drive.. Which is what this tool can do, if the driver a usb wants because it got it before it will assign it a different drive so that yes it will be usable!! Or how about you just assign your usb to c:\usb -- so that guess what its Always available no matter what else you assign to your drive letters.
The tool does fix your issue, your issue is the driver letter the system is set to assign your device is in use. This is not freaking rocket science
"I could spend hours and hours and hours and hours trying to figure out what's going on."
Installing a piece of software to autoassign unused drive letters is not hours and hours. Nor is fixing the registry so that your usb device does not get a letter that is been assigned to something else.
Here see my camera is assigned F
Now if I disconnect it and assign something my other disk (stuff) F -- guess what happens
Here it is in the registry before where it likes F!
Now it likes G -- every time I install it it will be G, unless something else is assigned G. Then it should auto assign it something else.
So either you got a permissions issue on your reg key where your account can not delete or change the old keys, or something else is going on - but it sure is not going to take hours and hours to fix it. The software I linked to takes the account permissions on the registry issues away. And can be used to make sure there are not conflicts, etc.
Or how about just delete the old key that assigned your usb device to D??
See I changed D and used up E and F, etc. So it gave my camera (usb) G now.
And that is what is in the registry, and that is what it will always get unless I assign G to something else.
Taking a few minutes to understand how something works, can save you HOURS and HOURS and HOURS of having to reinstall you OS ever time something is a bit out of place.