This stop has happened 5 or 6 times in the last 45 days with different parameters. No new anything has been installed since building the system. The problem began when I installed an ECS RC410-M mainboard (2nd board is installed). It ran reliably as far as I could tell for quite a while (weeks) with the second board / cpu package. I've tried a different processor (current is D945, used P4 also) and different RAM modules (current 2x512 DDR2 533). Board vendor is no help, as is nearly everyone else I've contacted. Obviously the system can not be used in a critical environment. System typically runs fine. These boards were used by HP in the exact configuration I have built, I have a hard time believing the board alone is responsible, but I'm ready to scrap the ECS. Is that the only solution?OK, I took the leap of faith and swapped the mb, problem solved (1-16-10). I chose a board with the chipset listed by Intel to support the Pentium D 945 I had. Apparently, the last manufacturing run of the ECS boards used a component substitution from the original hardware and made the board less stable with high speed cpu's.1 person needs an answerI do too