Yea that would be the real stumbling block.  Conversely (I just took another look now), I'll also need a good picture or a guide to the inside of the Compaq itself.  And even that won't guarantee that the power supply issue will get resolved (pretty much guarantees it won't).  It was just a thought.  If I get a chance to go back to that place, I'll look more carefully for an associated mouse; didn't at all cross my mind that that's what the board was.