Unstable System...still

Here is my system:
GA-MA790FX-DS5 motherboard
AMD Phenom Processor
Sapphire Radeon 3870 PCI-E video card
Kingston DDR2-800 RAM (runs at 667 in BIOS)
Windows XP-64 bit
Antec Sonata II 550 w/PSU

Still getting random system crashes, it has failed at the following points:
During boot up just prior to the password screen
Immediately after entering my password
During resolution setting changes
In the middle of a download online
At various points while running memtest
At program launch

I took out and tried various combinations of my memory modules, still failed at random points during memtest, so I'm guessing it isn't my modules. (unless they are all bad-highly unlikely I think)
I have had the system running in safe mode and it has never crashed.
This leaves the motherboard, or possibly the processor?
I am not sure what else this could be.
Can't get it in for diagnostic with PC repair shop until tues, so I thought I would try to get any other ideas while waiting...
Thanks

Actually, I thought it was a driver from the beginning. It started having the problem (seemingly) immediately after installing the motherboard drivers. I updated the BIOS since, and disabled the RAID driver. All the drivers in the hardware profile are running OK.
What is the best way to find a problem driver?
This is a first build, and everything is brand new, it was up and running for several hours when installing the OS, then it started crashing after loading the Gigabyte software/drivers.

I will describe my board and how everything is connected just in case there's something else wrong...
Gigabyte GA-MA790FX-DS5
Top of board:CPU Fan (4-pin) connected to CPU fan
Top of board left of CPU Fan: ATX 12v 2x (8-pin) connected to PSU
Above PCIE A slot: NB Fan: Connected to top front 92mm Fan
PCIE A Slot: Sapphire Video Card
Sapphire Card directly connected to PSU
Nothing connected to PWR Fan slot
ATX connected to PSU
IDE connected to CD-burner
FDD connected to 3.5" Floppy drive
SATAII 1 to HD
SATAII 0 and 3 connected to DVD drives
SYS Fan 1 (below SATAII connectors) not used
PCIE 12V to PSU
SYS Fan2 to lower 92mm Front fan
nothing on GSATA's
everything else as labeled on board/cables
120mm rear fan directly to PSU
120mm fan came w/case, I added the 2 92mm fans

all connections double/triple checked

I reformatted the drive, reinstalled XP-64 bit and it was working fine. Installed Wi-Fi card and everything was fine, installed the video card drivers from ATI-got a message in window's that I needed "Microsoft Net 2.0" before installing the drivers. I started downloading Net 2.0 (x64) and got BSOD and could not get back into windows (couldn't load past BIOS config).
Will try another reformat and reinstall...
Should I install MB drivers first, then Net 2.0 (if at all), then ATI drivers?