I recently stumbled upon this nifty little tool
which lets you do two very cool things to a thumbdrive:
- Flip the "removable" bit (the bit which makes the drive show up as removable / fixed harddrive)
- Format a non-bootable thumbdrive in a way that you can boot from it (even when regular formatting and trying unetbootin etc. doesn't work)
It's from Lexar, so I don't know if it will work on all brands, but it worked on my Emtec and a no-name drive I got somewhere. Found it here.