If its designed to run on 12v, and you feed it 5v, odds are in your favor that it won't fry. It may not work, but it probably won't fry.
EDit: Looking at the pics, it looks like theres 2 wires on the harness... Red and black. Hooking to a PC, on a drive connector, Yellow is +12v and black is ground - TYPICALLY. Did I misunderstand the question?