my computer freezes after about an hour or sometimes earlier after bootup.. im not sure but i think it is my ram. ive got 2 rams...256 n 512mb ddr ram..when i boot up it says approx 490mb ram..this is cz 32mb is for onboard graphics..so i thk my 256mb ram is at faulty..however whn i use only the 512mb ram it still freezes after an hour or so...my pc screen jst freezes...the mouse / keyboard dont respond at all...