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

If its running in safe mode without crashing it might be a bad driver somewhere. Did you download anything new before the crashing started?

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 have had some issues with companies not posting 64 bit drivers (they like to hide em) uninstall the MB drivers, and get newer ones from the Gigabyte site (support, driver downloads) also be sure to run the @BIOS (it helps, I'm using a Phenom 9850 myself) sometimes the stability issue can be caused by the BIOS.

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

uninstall the mobo drivers & see if the problem goes away.

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?