Ok, So I just got a new motherboard, CPU and Ram. I bought a Gigabyte GA-M57SLI-S4 Rev-1.1, Amd Athlon 64 X2 6400+, 2 Gigz OCZ Reaper that is suppose to run at 3-4-4-15 @2.4V. I have a BFG 8800 GT OC2, but that was in a previous system running perfect. I Also have a OCZ GameXstream 700W PSU- all voltages are at right levels. I got all my new stuff and formatted my hard drive and put windows XP on. I noticed my ram was at the default bios setting of 5-5-5-15, so i decided to go into my bios and maunaully change my ram timings to what they should be, 3-4-4-15 @2.4v, however when I tried this the computer would not boot, and I have to reset the cmos battery. So I manage to get the ram at 4-4-4-15. I try to play COD4 and Crysis, but they both crash after about 1-2 hours of play. So I put everything in my system back to default and the same thing happens. I ran Prime95 for 8 hours with no errors. So I thought it was the ram so I just ran memtest and that came back with no errors as well. I still think it may be my ram... Does anyone have any idea what my problem may be? Any help would be greatly appreciated.