BigDaddy, I cannot say if your MemTest will fail. I suppose if it really is a memory problem perhaps only MemTest will find it. I do think the others could also. I think there is a version of MemTest that runs under Windows (never used it). It cannot test all of memory, of course, due to the presence of Windows. Please be sure to try Prime95. It was the one that exposed a HW problem on my XP x64 machine. Is there a chance that the machine is dirty inside? I have seen (and heard) machines that were full of dust and cat hair - burned up the CPU. Some BIOS codes will show various temperatures in the machine. If someone could look, it might prove useful. Did you run HyprPi against all four cores at the same time? Good luck, John. machine is brand new. I assembled it. HyperPi was run against all 4 cores naturally. Prime95 also did not return an error. Thus far I guess the only thing is if MEMTEST86+ will show an error. But I am more leaning towards Cool'n Quiet. Because this only occurs when the CPU is idle