System Reboots with ATI 9700pro

I have Asus p4g8x motherboard and ATI 9700pro. I have 1 GB of ram, SB Audiology Mp3+. CD-RW and CD-R. Problem – The system reboots itself 2 to 3 times in an hour. I have all the newest drivers and new bios. Changed the motherboard, power supply (450W). Turned off the fast write for ATI. The only thing that seems to make the system more stable is when I turn down the AGP to times 4. I know a lot of people have the same type of problem with this configuration. ATI claims that they have no problemwith the card, but some boards are saying different. If anybody has any type of input on how to fight this problem I’m listening. Thanks