HDD cause system restarts?

Heya guys, only my second time here so my bad if this is the wrong place to post. my specs:gigabyte 965p ds3 rev 3.3, evga 8800gts 320, bfg 650watt PS, 1x2gig of corsair ram 5-5-5-12, WD 250 7200 HDD intel e6300 1.8(clocked 3.0 stable), well when i put my new system together ever thing was great, no problems, then the one day i turn it on, ever thing went to hell as far as restarts all the time freezes and of course, the blue screen of death, i replace the power supply from 500watt to the 650 bfg, replace the battery on the mobo, and everything was fine, then i looked in the case and saw a connector was burn, hmm yea not good, ive refomated so many times to the point that were if i go to down load upadates for xp, the first update after a format i get a restart, i get the blue screen saying, error for third party drivers or parts, got a windows error for ram, so many memory dumps i dont know what to do any more. i dont want to buy a bunch of parts i dont need,im thinking a bad HDD but who knows. thxs for the replys in advance