XFX Geforce 6600GT reboots machine

I tried one of their bundled games - EA sports Nascar - and it reboots the
computer every time. It also happens frequently during games of Pirates.
Changing to lower res does not alter this behavior. I downloaded the latest
driver but still no luck. Any ideas? I sent XFX an inquiry and I am waiting
for them to answer.

I run XP Pro with an 8x agp board with 512MB and P4 2.8Ghz

J