Suddenly boot problem - no post - then crashes in windows

Question

hi there! first off, here's my system:
P4 2.80C @ FSB 200 HT enabled
Corsair DDR400 2-2-2-5  
865PE Neo2-LE
Sapphire Radeon 9500 no OC
Chieftec 360W
Western Digital 120GB & Seagate 20GB no RAID
BIOS - default settings
WinXP
Alright, my system has always worked fine in the past, but yesterday it started acting up, making more noises than usual, CPU working hard at low workload, and things generally being slow. This morning when i turned my PC on, it showed the first boot page, but wouldnt continue, post or accept any keypresses. I turned it off and tried turning it on later, and it was able to boot completely. So i was in windows, and everything was moving slowly. "My Computer" wouldnt open, my browsers would crash and i wasnt able to launch any games or benchmarks. then - BOOM - the computer turned itself off. so i startet up again, suspecting a virus and whatnot. A friend said it was probably that winBLAST thing that was going around earlier. so i tried to remedy it by doing "shutdown -a", and running a symantec blastfix.exe, which didnt find anything. i started a full virus scan with norton 2003, but didnt make it all the way through, as the computer would crash at some point. not at any special event, just after a random amount of time.
Hope that's enough information, will gladly supply more if needed.
bry - out

Answer 1

Check if your CPU Fan is failing as overheated CPUs will caused smiliar problems. Also check for other hardwares if they are burnt or suspicious of overheating.