Most would say yes, but I say no.
If you are running XP, you have two options... either perform a repair install
or use Sysprep
to do the trick.
If you are running Vista, the repair installation is not an option as MS did not include it with Vista. I cannot find anything regarding successful use of Sysprep with Vista. It may work, it may not. Vista does have a repair option
, but it is not the same as the XP version.
Basically, if you are running Vista, you may end up having to format and reinstall. If it were me I would give it a shot, but I would prepare for a complete install beforehand.