I know how to get to DM, and how to assign drive letters, but is there a way to search a hard drive for the remaining space?
A few facts to throw out and see if the apply to you. Some old bioses have a hard time reading drives above 137GB, because of this, there is a jumper setting to limit a drives size to 137GB. Check your drive and see if this jumper is accidentally set. If it is not check back in the bios and see if it is reporting the full drive size or only 137GB. If so, it may be limiting it to 137 (with an occasionaly flash of it making it through I dunno). My guess though is the jumper.