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