I am completely lost in what to try next.
Here is the Gear:
EVGA 123-YW-E175-A1 LGA 775 NVIDIA nForce 750i SLI FTW ATX Intel Motherboard
OCZ Platinum 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model OCZ2P10664GK
Intel Core 2 Duo E8400 Wolfdale 3.0GHz LGA 775 65W Dual-Core Processor BX80570E8400
ASUS P5A2-8SB4W 80mm Sleeve CPU Cooler
Raidmax Aztec PC case
Asus 1080P LED monitor
Windows XP 32 bit
The graphics card was an EVGA 7900GT left over from my previous build as was the 550 watt Antec power supply.
I only play a few games and ever since I built my PC back in early 09 and I have always had a few weird issues.
1. random times the machine would get to the point just before the windows logo at boot and then reboot automatically. This could happen up to 4 times in a row. Initially it happened alot and over time it happened less and less until about a year ago it just stopped.
2. When playing WOW in full screen mode even on low settings the game would randomly become these wierd flashing patterns of colors. I would go back to the home screen and back in and this would fix it. This happened very frequently so I switched to windows full screen mode and that fixed it. Sometimes this would happen and it would be a complete and total lock up and I would have to reboot. I have had WOW on low settings for my old monitor which was 1440x900 as well.
3. Every so often, either at boot up or while in a game, these strange horizontal lines, that are equally spaced and are shimmering silver like tinsel on a Christmas tree would come up over the entire screen and would be in a little block over the mouse cursor that would move with the mouse. Other times the lines come up just over icons, and pop up windows. but not over a consistent background color.
4. Rather using a USB or analog audio headset on any port, there is always a low level background buzzing that never goes away and does not seem to raise or lower with external volume adjustments.
So the machine was in a harmonious balance of terrible, but I lived with it.
In December I got star craft II and within 10 minutes of playing, the weird color freak out I got with WOW happened. It happened a lot. So I put it into windowed mode and all was well just like it was with WOW.
However the verticle line issue happened A LOT more often. The lava level was relentless for this. It was such a pain to get though. ALso I started screwing with WOW and found that on higher graphics setting the issues happened more often.
I downloaded HWmonitor at this point and found everything was running well within acceptable limits and nothing was getting hot or anywhere near it when the freak outs happen.
I got through the game this way and then picked up SWTOR. The game was livable on low settings with shadowing off but I figured it was time for a new Graphics card. So having always expecting my graphics card was the culprit of all issues, I picked up:
GIGABYTE GV-R685OC-1GD Radeon HD 6850 1GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX
With the new card SWTOR frame rate was better and the game play is too but its way less then it should be.
About every tenth step, the game hiccups for a millisecond even through my frame rate is reporting around 50 +. I can put the game on Low setting and the hiccups get better, the frame rate approaches 100 but its still obnoxious and no where near smooth enough.
After this I did a benchmark test with Benchtown. The major concerns I saw was the the 2D graphics reported in the 400's. I disabled everything on the machine in admin settings and still I could not get over low 500's. The hard drive mark is pretty bad too at about 400.
I have douched the machine with Norton anti virus, CC cleaner, and malware bytes a few time. I also ran a defrag of all drives and updated the graphics card and mobo drivers, and updated the mobo BIOS to no improvement.
So now what?
I am tempted to just get a new power supply, Mobo, case, processor and memory so that everything is new but I know that my E8400 is more then enough to handle the light gaming I do.
Also I have tried overclocking it as well to make sure it was not the processor, and that also showed no improvements.
Could be that both cards are bad (Not likely). Most likely #4 is interference from one piece of hardware or another. Or it could be your sound card being cheap or failing. Either way, probably not a relevant aspect to your larger problem.
Like esrever said, run memtest86+ (the normal version is a bit buggy from what I hear) several times over. I like three, but all night is even better. If you come back with errors, it could very likely be a memory problem.
Not that I know of. Your mobo might have come with a disk you can try to boot into and then it may have a test application on it. Another thought: when you get a new mobo you need to install Windows on it again.
You COULD reinstall Windows and test. Last resort before buying a new mobo...