So about 6 months ago, I began having (or noticing) problems with my old system. At POST, it would power back down after a few seconds. This would continue, and the interval of "time with power" would increase until it finally booted up. Replaced the thermal paste under the cooler with no change. I decided the PS was probably bad, so this tax season I ordered a new case, PS, RAM, HDD and a new Vid card. Replaced all those parts and did a fresh XP install (sp3). After a few days the computer started randomly shutting down, no BSOD, and again, wouldn't start properly, same symptom. Deciding that I must have been wrong about the PS, I ditched the old CPU, mobo, ram, and the new vid card for all new stuff. So this is an all new build, in essence. Random shutdowns. No rhyme or reason to it. No viruses, according to AVG. No heat problems, at least the mobo software says so. CPU is around 40c, up to 50c max under load. (new) Memory tests fine with memtest86 and windows mem test discs. PS is a coolmax 600b, should be more than enough for what I'm running, and is certified for my video card (3850) The only remaining common elements are:Soundblaster X-fi, external USB My book, keyboard, mouse, wireless USB adapter, power strip, and speakers. Is it remotely possibile that one of these things is causing my problem? I just can't imagine how they could. Ideas?