FFXI Crashes ComputerFollow

I've been having problems for about 4 months now with FFXI randomly shutting down my computer. This isn't just cutting out to POL, dropping to the desktop, or even rebooting. This is the bad kind where it sounds like a mini-bomb went off in your case. BOOJOOOOM! Sorry for the sound effect. It's really bugging me for a couple of reasons. 1. It almost never happens during other applications. I think in the last month it's shut down once while running other programs, but at least 3-4 times a day with FFXI; 2. It usually only happens when I change areas in game, or occasionally when there's a lot of stuff on screen; 3. Computer won't restart right away after it shuts off. I usually have to flip the kill switch on the power supply, let it sit for 30 seconds, then try turning it on. Otherwise it'll start the boot sequence and blow again; 4. The shutdown is usually accompanied by revving up of the hard-drive (a sound I have come to loathe).

I run adaware/spybot all the time to make sure my computer's clean. I've got McAfee Virus scan. I run defrag, scandisk, and disc cleanup a couple times a week. I can't seem to figure out the problem. Please help :)

Specs:
Processor- Athlon 2200XP+
MB- ASUS A7N8X Deluxe
Ram- 512 MB
Video- Geforce 6600
Sound- Onboard
Hard Drives- Western Digital 20GB (5 GB free)/ Western Digital 40GB (7GB free)
Power Supply- 450Watt

Hi there,

it may sound strange but i had once a almost similiar situation with my pc. The difference was that the shutdowns also occurrs sometimes with very strange error messages. One part was the same, it almost shutdown when FFXI was active.
The problem was caused through the fan from the graphic card.
The fan was full of dust which leads to overheat and then the strange shutdowns. The reason that it only affected my FFXI application and no other application was that FFXI needed much more arithmetic operation (power) then the other application that i used at this time.
Maybe its the same prob with your PC, just kill the dust from your fans.