ATI 9700 AIW issues

Hi guys,

I have recently bought the following system and I have a major issue with my VGA card. In 3d games such as Mafia, C&C renegade, Warcraft III etc, my system reboots randomly during the game. I have installed XP service pack, Catalyst 3.0 drivers for AIW 9700 pro, Nvidia 2.03 drivers for motherboard,directx 9.0 and the latest audigy drivers but the problem still persists. I have tried different combinations such as low quality high performance settings or vice versa but the problem still remained the same. I have cancelled the Agp 8x support from bios and gave her a go but it did not help either. I have checked the IRQ seettings from device manager and there is no conflict there either!!!
I have also used 3d MArk 2001 Se and my card finished the tests normally. So everything seems to be in order but my system keep on booting after a while (or freezes in mafia for ex) while playing these games. Can you please give me some advice cause I am seriously about to go insane after doing everything I know to solve the probem but not being able to do so... (especially paying 600 cad for getting some performance but not even being able to play a game without a problem is so frustrating...)
By the way here is my configuration:

Samsung 550b 15 inch Monitor
Asus A7N8X Deluxe Nforce 2 Motherboard
Amd Xp 2100+ Cpu
512 Mb DDR 333 Mhz ram
All in Wonder 9700 Pro VGA card
Creative Audigy Soundcard
40 Gb Seagate 7200 rpm hardrive
Case: UL-550 ATX Mid Tower, 2 x 3.5" & 4 x 5.25" Drive Bays, 300W P4 power supply & 2 USB Ports in Front,Blue Trim faceplate
LG 48x24x48 CD-RW
LG 52x CD-Rom
Cicero 16X DVD-rom

ARRGH! Everywhere I look, you're there! How many times have you asked this question dude?!

Anyway, looks to me like PSU. You've got a lot of goodies in your box, and if that's a bog standard generic PSU, pound to a penny of pigshite that's your problem.

get a better PSU or try reinstall of XP or conflict between Nvidious board & the ATI card... that are the most likely options to find your problem (in that order I believe)

Hmmm, wonder if I can get a valid page fault ???
these invalid ones are far too commonplace...

Here is the latest situation...
I have tested my system with the 3.1 catalyst drivers and the problem seems to be there despite the fact that it is occuring less frequently now. I have been monitoring the voltage when I am running the 3d games and realized that +12 V voltage goes to 13V during high cpu and video card activity. Besides my psu seems to have a peak of 300w rather than a stable output of 300W, therefore I am almost certain that psu is the problem. I will be getting an Enermax 450 watt psu in about 2 weeks time and will see whether things are ok or not then. I will keep you guys informed. I have tested my rams and they complete the memtest-86 v 3.0 and for the 3d Mark 2001 I can complete it sometimes and other times rebooting or crashing is what I encounter with  

I am sorry for posting the same thing everywhere but I am sure you can understand how frustrating it is to have a certain knowledge of pc and trying everything I know to make it work but not being able to do so after a constant effort of 3 weeks!! All those guys with radeon 9700 pro's that run smoothly, I envy you  ) Thanks everyone for their suggestions, I will hopefully solve things with a new psu...