Problems with USB thumb drive

[Charlie98]

I have a 32GB Silicon Power thumb drive that I use to shuttle files between my desktop and HTPC. The other day I was downloading files to the HTPC and it just disappeared as a drive. I've reformatted it, I've wiped it with Acronis and reformatted it... but nothing I do will allow it to be seen as a drive on my desktop PC. It shows up in Disk Management, where I can format it, etc, but it will not assign it a drive letter (and probably why it doesn't show up as a drive on the computer.) It does, however, show up as an available drive on the HTPC... what am I missing?