computer freezes at boot and during windows

Here's the problem: Boot up the cpu, and it will hang at different points along the boot process. I usually have to restart 3 times or so until it gets to windows screen and then i'll have to reset once again. Then the computer is fine. But it will always hang when playing Battlefield 2. Sometimes after 10 mins sometimes after 30. Some days, the computer doesn't hang all that much. Yesterday, after I defragged, and chkdsk, the system only hung a few times. But today it was ridiculous.

processor: E6600 2.4 G core 2 Duo
Ram: Adata Vitesta ddr2 800 pc6400 (2 x 1 Gig sticks)
psu: 500 watt NZXT pf-500 2.0 psu (psu is generic comes with case)
hd: 320 gig partioned SATA (generic i think) (2 partions)
Windows XP SP2
mobo: Asus p5n32 Sli SE Deluxe
video: GeForce 7900 Gt (256 mb)


Things I've done: Taken out one stick of ram. Computer doesn't freeze as much, but after a day or two, it becomes to freeze again.

tried running mem test: computer always hangs w/ 2 gig's in there. Can't get through mem test.

Updated video card drivers (version 93.47 from NVidia)

Loosened memory timings (5-5-5-15 and 5-5-5-18).

Ibuypower.com is sending me a new hd and ram b/c they're not such whats wrong.

ANy takers ? It would be very appreciated.

 

I'll take "two bad RAM sticks" if there's a pool started on this.