Have a punt at it anyways.. try windows update website, the apple website etc.. If they're of no use, then maybe look at Mac enthusiast sites such as OnMac and look around the forums.. (by the way, haven't been to that site yet, discliamer )
Try and remember what settings or things you've installed that have changed from when it was still stable. You may try using system restore, but its a hit and miss situation, and sucess is not garunteed as such in this scenario...
Or maybe one of the guys/gals here who've XP'd their Macs can provide a little input?