Now for the general troubleshooting question for anyone who might be interested or has a good sense of what might be going on...
I don't actually know if the problem with my computer is the power supply (it is a Fortron Sparkle 400W)...but it could also be my motherboard. I figured that trying out the PSU is the cheaper way to find out, since if I got a new mobo I would buy a new CPU, and I may also need new RAM.
As I said earlier, my computer is nearly exactly 3 years old (got it in Aug. 2006) and you may as well consider it to have been running for about 9 hours everyday. Not only did I spend a lot of time on the computer playing games, when I'm not using it I tended to leave it on as well so it has suffered a lot of abuse.
The first signs of problems began about a year ago when I'd turn it on, and sometimes it would freeze on the Windows XP logo (so I'd have to shut it off, reboot, or go into SafeMode before trying again in Normal setup etc.) Then, around this Jan. 2009, after trying out Team Fortress 2 (which my computer REALLY struggled to run--lowest graphics settings and res would yield 20-30 FPS on a busy public server) I started getting terrible display artifacts (even on my desktop or while surfing the web) which eventually led to a few days' shut down and a video card replacement (the video card was the confirmed immediate culprit at the time, since taking it out and installing it into my brother's computer wouldn't work either.) To this day, however, I still don't know if any other problems with the PSU or mobo may have caused it to fry (it was a BFG Nvidia 7900GT 256mb), because my motherboard's fan was VERY noisy at the time, making sounds like a mini leafblower. Either way, I avoided playing TF2...
...until about 2 weeks ago. One of my buddies recently got a new computer and was thrilled he could play TF2 without lagging to death, so I wanted to follow him to a few servers and join in on the fun. AGAIN it seems to have taxed out my computer because the following day I kept getting the MACHINE_CHECK EXCEPTION blue screen of death and noticed that the mobo fan had stopped. Sometimes I could turn on the computer and the fan would run, but after about 5 minutes it would sputter and stop again, and cause MACHINE_CHECK_EXCEPTION.
This past week I've been trying to patch up my computer to some working level...and these measures have each failed:
1) Replaced the 40mm mobo fan by attaching a new one to the same outlet right on the mobo - same thing would occur (work for 5min, sputter, and stop) so it's not the bearings on the original fan.
2) Yesterday, my brother brought home a little adapter wire thing, which allowed me to take the original mobo fan and supply power to it directly via one of the cables from my PSU. So it worked fine yesterday, had a lot of fun catching up on my gaming fun (Quake Live, not TF2 ) However, I turned it on today and browsed my e-mail and internet for about 10 minutes, and then these artifact stripes showed up on my screen and my computer froze. When I try to turn it back on, all the fans etc. seem to be working but my computer won't turn on.
So I'm just curious: do you think it's mainly the PSU, the mobo, or PSU-fail-induced-mobo damage?
I know that I could buy a whole new system for pretty cheap these days but my mother is a control freak and is likely going to shut off my internet for the upcoming school year, so it would just be a colossal waste to have a shiny new computer I can't even game on for 9/12 months.
Go with the Antec avoid modular and upgrade both your cpu and get more ram 2x1g,for that 7900 video card you need more that 2.1 ghz..........~~~~~~~~~~~
OTOH,,,, you have a 939 mobo and it is taken you about as far as it can,so maybe it is time that you considered a future replacement,the machine_check exception is almost certainly a hardware message either not enough or failure of some kind or another or a combination of the two..