Here’s the scenario. You have this PC, its unstable, but you have ran all the proper diagnostics and cannot come up with an issue… When was the last time a software issue cause a hard lock of a PC? That’s right it hardly happens. Your diagnosed the hardware, but you’ve been leaving all the same interconnects in i.e. power cables, ide cables, sata cable, etc. I have seen in the past a system running, but being unstable because of a SATA cable, so replace the cable and re-run the tests, set the PC through its paces. Sisoftware has a pretty good burn-in utility that can stress all the major components. If the PC makes it through the burn-in, then your in the clear…or are you?