you might have 2 devices trying to use the same drive letter in windows.  I've had that happen before.

right click on my computer and go to "manage"
navigate to storage/disk management.

find the pre there, and change the drive letter to something high up on the list..I use "P"

it'll warn you that some programs won't work after doing it and blah blah.  do it anyway.

you're done

Sometimes when you use thumbdrives and such, the computer will try to give the same drive letter to 2 devices.