I replaced my sister's motherboard on her compaq with a replacement from HP.  Computer locks up 2 minutes after startup.  Tried a non-destructive system recovery.  Computer stayed on for a 1/2 hour to a hour while I reinstalled hardware and Office XP.  It then froze again and kept freezing within 2 minutes after startup again.  Is there any command to reset all the devices?  Or am I just going to have to reformat the HDD completely?