continued freezes

Hi guys,  Been a while since I have been on here.  I am at my wits end, so bear with me.  I ordered my rig in August and had problems from day 1.  Initially both memory sticks were bad, then the video card.  DS replaced my RAM and refunded my video card.  I bought a new card.  Since the beginning the computer will periodically freeze on the screen requiring a reboot.  This may happen within 5 seconds, but more often within 5-30 minutes depending on luck.  It used to happen frequently on pages like facebook, but could also happen while editing photos.  I have tried everything I know and maybe I have made the problem worse.  I have run memtest on each card twice.  I have a new video card with new drivers, a new mouse with new driver.  I thought the problem might be vista 64 bit.  So I backed up all my data and installed xp over vista and it still crashes.  It wont even let me load up office 2007 completely prior to crash.  Sometimes it just freezes, other times it beeps when is freezes(less often).  My 2600 dollar computer has been reduced to an emachine in 15 minutes blocks.  I have run virus scans, malwar scand, adaware and regcleaner.  Any advice or do I need to send this baby back for repair.   Thanks for any advice.  I may be done with this thing for a while. Here is my config:

I was worried about the mobo or some virus that I cant detect