PCdoc: Yeah I moved all the files I needed from the drives and disconnected them. Not planning on hooking them up again.
patio: There was one yellow ! for an "unknown device" in a USB slot which turned out to be my external harddrive. I've unplugged it now and will let you know if I get any more BSoD's.
Do you think this could have been the reason? It usually works most of the time, and works on boot, just sometimes after using the computer a while it becomes unrecognised?