Re: RTW encountered an unspecified error and will now exit
It sort of begs the question, if you found 4 unused PC's, what the heck else did you find? Not sure I really want to know the answer to that though 
Other than the graphics memory being a little on the small side it should just about squeak by, the problem with unspecified errors is that they don't give any more information because they can't. It's crashed in a way that no information was available. You could try looking in the event viewer but it's been a while since I used XP and can't recall exactly how to view it, and it may not give much more information.
I'd suggest asking in the Basement - the real windows experts hang around in there and they may be able to help, and also try the RTW Tech help here as this is more RTW than RS.