Random Restart Help

Hi,

I have had my PC for about a year now. I selected all the parts with the help of my local PC guy and got him to put it together. Not long after i first got it i tried using Ai booster. And i changed something, either the CPU voltage or the FSB (not sure now), and it restarted itself.

Specs:

ASUS A8N-E
Athlon64 3200+ 939 (venice i think)
2x512mb ddr400
120gb IDE
Ati x800 Pro
CD-ROM
DVD Burner
Auriga 400W MPT-400 Power supply
Netgear Wireless Network Card and a 56k Modem in Pci slots
2x case fans

It origianlly came with an X300 SE, but i have recently changed to the x800 Pro in the last couple of weeks.

The problem is that it will restart itself every now and then, completely randomly. Sometimes a few times a day, sometimes only once, or none.

I used to network it with a crossover cable to a laptop, and every time i plugged the network cord into my computer, it would restart. It would also restart if i had the network connected and then i tried to dial up to the internet. Now i use wireless and it doesn't restart when i connect with the wireless.

It doesn't matter what i'm doing; using the net, playing music, gaming, or even if i'm not using it and its just sitting there on the desktop screen with nothing running, it could restart at any time.

I did notice that the CPU voltage was running at a little over 1.5 volts, and when i checked the specs of the CPU at AMDs site it said it should be running at 1.35-1.4 so i lowered the voltage to about 1.36, and it restarted much less than it was before. Then the restarts increased again, so i now have the CPU voltage set on AUTO through the BIOS, and it is sitting at 1.392. It restarts less again now but it still does every now and then, probably a couple of times a week.

Anyone know what this could be, or experienced something like this themselves? Could i have fried something when using Ai booster?

Sorry for the long post.

Thanks for any help!