any overclocking? How about irq conflicts? Is there a situation where it seems more prone to lockups than others? What is the cpu temps? Have you adjusted the pagefile , or possibly are running without one? How are the power supply rail voltages in the bios, seem low or high? When you reset the cmos , its possible that the memory timmings are defaulted to an aggressive setting , make sure they are in spec with the ram , or back off the timmings alittle bit. There are alot of different things it could be but if the cpu temp is good , id look at the memory next , then the psu . Good luck , sorry this reply is all over the place , im medicated hehe 38