My main PC, an 8-year old Dimension 2350, started powering down randomly today (as in monitor says "no signal" and all power is cut, and NOT the progressive Windows shutdown that happens you mistakenly push the power button.)
I'll be looking for obvious issues like loose connections and capacitor bulges/leaks. I think there was a very slight burn smell from the power supply a few days ago, though there's none today and the PC has zero issues turning back on. It will run for 1 to 3 minutes before shutting off and it's supposedly slow, but I couldn't immediatly check what threw it to 100% usage without elevating the Taskmgr. I replaced the previous power supply 3 years ago due to a less hidden smell AND reboots.
I recently noticed prominent lint covering some vents and hadn't bothered fix them then --that DOES increase the CPU temperatures and cause shutdowns AFAIK (Pentium 4 @1.7Ghz by the way). I should run Prime95 stability tests as well. It doesn't have more than the stock heatsink/fan combo for normal cooling and there are no CPU temperature sensors to confirm whether overheating is a problem, but it's been OK at that spot of the house for 3 years. I haven't checked the PCI nVidia card's sensor today but know that particular part is about 50 Celsius on idle and 70 under heavy loads. The card is an 8400GS and the PSU is 350 Watts. The former PSU was rated ~100 Watts back when I had an older nVidia card, so the card should not be choking the power distribution --nothing is even running in 3D when it dies, and heavy 3D games/screensavers haven't been a problem before.
The PC also powered down while I was spying BIOS settings and another time while booting Linux, so I know it's not XP's fault for once and unplugged it till I start checking. I see no "thermal events" nor anything else in the BIOS.
What else might I check? can I finally justify building a custom PC? Thanks