I installed a new 1.5TB drive today with no issues. Later on I noticed that my drive M: (1TB drive) was also showing up as F: Also a 750GB drive is showing up with another drive letter. Drive C: is fine, no dups. The box is very basic, it just runs XBMC for video streaming.
I tried changing the drive letter (M to a different drive but the phantom drive F: persists. I rebooted but no better. I googled around and did the regedit for MountedDevices but that did not help. Drive management only shows the real drives, no phantoms are there.
System restore was not enabled (Yeah my bad ...) So that's not an option.