We had the same thing happen when we put XP Pro on this system. I think what happened was the hard drive wasn't completely wiped when we tried to reinstall. I don't know if you're using the upgrade or the full edition, though. Once we fireballed everything related to Windows off and started clean, everything ran like a dream. We also use the shit out of McAffe, haven't had any crooked shit happen in ages. *knocks on computer table*