Okay, first post here. Hopefully someone might be able to give me a clear answer.
I built this computer at the end of summer last year. ECS nForce 570 SLIT-A, Celeron D 356 with Mascool heatsink/fan, 2 GB OCZ DDR2 @ 667MHz, EVGA GeForce 8400 GS, 60 GB and 80 GB hard drives. 350 Watt PSU, but underpowered on the 12V rail, which I knew beforehand - and never got around to replacing (stuff comes up!). Added a 320 GB Seagate SATA a few months ago. Currently connected to a Acer X243 Widescreen via DVI. Nothing overclocked. Windows XP Pro, SP3.
Not the best system around, but I just needed something that worked to replace the HP that was fried in early 2007. I play a lot of games (shooters and RPG's, mostly), but I'm not obsessed with getting the highest resolutions, ridiculous frame rates or such. If I can max settings in a game, great. If not, playable and decent looking works for me. And it works fine with the 3D stuff (modelling, texturing, rendering).
A while back, my desktop started to look funny and seemed to be getting worse. I powered down and opened the case to see if there was any major buildup of dust (which is one problem I do have with the computer). Nothing noticable, so I put the panel back on and restarted. Ugly green screen. Shut down. Restart. Nothing, so I hooked the monitor up via VGA instead of DVI. Worked, but darker and not as sharp. Rebooting didn't cause problems, but a cold boot required me to hook up a CRT first, then after I was in Windows, I could hook up the Acer.
This got old quick, so I borrowed a bit of money to get a different card (thinking that was the problem, and I wanted a better card anyway) and get a better PSU. Finally selected an 650 Watt from Ultra (with 38A on the 12V rail) and an XFX 8600 GT XXX (with the Zalman fan/heatsink). Other than triggering Windows activation, install went fine. Had one crash in Bioshock after starting a new game. Didn't bother with any other games at the time, had other stuff to try to get done instead.
I ran some of the nVidia demos, just to see what they were showing off - and before I had the 8400, the best I had was a PCI FX 5200, which I believe was KIA when the HP it was in fried. Nalu crashed after a while and the Toys demo didn't fare any better. And lo and behold, my display started to get a bit garbled. I wasn't happy. After my system froze, I shut down and waited a few minutes before booting up again. Garbled display, 640X480 resolution, 4 colors. Not quite what I had before (1920X1200). Getting less happy.
Put the 8400 GS back in. Things seem fine.
I don't have another mobo with PCIE to see if the 8600 GT is borked or not. And I'm wondering if I really needed the card, if the 8400 is working now without a problem.
Sorry for being long winded. Just thought it best to mention what I've got and what I've gone through over the past couple weeks.
Would an underpowered PSU have done this, and the new Ultra was all I needed to get my computer back under control? Or could the fact that the GT is a PCIE 2.0 card and my mobo only supports 1.0 be why it stopped working? I've seen conflicting answers about the backwards compatability - some say a PCIE 2.0 card will work fine in a 1.0 slot (just not as fast); some say it works in a 1.1 but not a 1.0.
Any ideas?