I have had my system for about two years, upgrading along the way. When I first got my XFX 750i mobo, the first and third DIMM slots were shot(I called customer support and they said I may have a faulty RAM controller). Since then I had been using my 4 gigs of ram in the 2 and 4 slots without problems. When I upped to a Q9300, my PC only detected 2 cores and one L2 cache. I never figured the problem out, and my PC worked fine with just the two(currently kicking myself in the face for not getting a replacement)
Recently, my system started freezing in 3d Apps, but then it started locking up while idle, then stopped booting all together. I unplugged it, rebuilt it, and let it sit over night. Next boot got to desktop, then video driver(9800gtx+) crashed and recovered every 5 seconds(literally). I have swapped out all components including my PSU(which has enough wattage/amperage) and RAM.
The 750i has a debug LED and CMOS reset button on the I/O panel. The codes kept saying my RAM was not initializing, but I swapped out with good RAM and the same happend.
When the PC would turn on, for about .5 seconds it would have the "loading drivers" sound and then not post any video. The HDD led would not show any activity, however the drive was spinning and works in another tower. Every once in a while, after sitting for hours, I would get one boot to the "starting windows" screen and the computer would lock up--nothing.
I'm almost positive this is my Mobo causing it, but I want to make sure before I go buying a new board, after all 775 mobos are extremely expensive now compared to a year ago.