RTCW freezing with new video card

CPU: P4 2.6C @ 3.25GHz (fsb250)
MOBO: Asus P4C800-E Deluxe
RAM: 512MB OCZ Dual-Channel PC4000
VIDEO CARD: Chaintech FX5900XT (390/700)

I just got my new FX5900XT and it is awesome, compared to my old MX420. I'll be playing Return to Castle Wolfenstein and about 10-15 minutes into the game the computer will freeze up. I can't move the mouse or do ctrl+alt+del or anything. No blue screen, no nothing, IT JUST FREEZES! CPU runs at 49C under full load, and the video card runs around 52C. AGP voltages is set at 1.65 I believe and that other AGP voltage setting (forgot what it is called) is at 1.6. This never happened with my MX420, so what's going on?

Have the latest drivers? Does only Castle Wolfenstein crash, or do you get crashes from other times of high load (other games)?
Those temps do seem a bit high, can you increase your fan speeds and/or reseat your cpu fan using some good arctic silver thermal paste?

Yes, drivers are fresh from the Nvidia site. RTCW is the only game I play, and 49C for the CPU is normal under that load. I am getting a new heatsink/fan for it though. What about the AGP temp? This has only happened since the new fx5900xt. I'm hoping it's just a voltage setting problem. I have AGP voltage set at auto and 1.5. Any other guesses?

Ok, it happened again, except this time I got a blue screen. "IRQL not less than or equal", that seems like a driver problem to me. I'll try reinstalling the video drivers.

My Computer is
Abit AN7 NVidia nForce2 Ultra400/MCP-T Chipset
AMD Mobile 2400+ @2350 Mhz 35c/41c
Gigabyte ATI Radeon 9600XT Video
550 Watt PS
Thermaltake Silent Boost CHS
1 CDR RW
1 CD Rom
2 HD 100 gig and 60 gig 7200 RPM
Windows XP Pro

I have an Abit AN7 Mobo for AMD, it has an AMD Mobile 2400
and I had an nVidia GeForce FX5200 Video Card before and I just got a Gigabyte ATI Radeon 9600XT Video Card. I installed the right drivers from Gigabytes site and tried ATI's drivers for it.
Nothing seemed to work, I was constantly freezing up and having blue screens. SO, I got a little smarter and removed the old video drivers completely from my system, or so I thought, I hadn't removed them before (duh...).
At least when I used the Windows XP Pro - Add or Remove Programs and removed my old NVidia graphics drivers it seemed to work better. It wouldn't freeze up so often and same with blue screen, not as often. That is not everytime I turned on my computer for more than 5 minutes, it went for at least 15 minutes before freezing, or blue screen.
So I just moved all of my files I wanted to save from the Windows XP install, like My Documents and Favorites, stuff like that and I put in my Windows XP Pro disk, set my bios to boot from CD and went through and reinstalled Windows XP Pro into the old Windows Folder, it asks in the sequence if you tell it you want to install XP to the same C Drive, if you want to first delete the files in the C:\Windows folder and install a new copy in that folder and I said yes. So I set up Windows XP Pro again.

My Abit AN7 Mobo is based on the
NVidia nForce2 Ultra400/MCP-T Chipset so I have NVidia drivers for most everything else but the Video Card. So, I installed the drivers for my ATI 9600XT card first, before I installed the other NVidia drivers for the rest of the Motherboard.
Now my computer is working like its supposed to, at least, now it is. Only been 18 hours so far and it only froze once when I OC'd it too high and ran MS Combat Flight Sim 2.
But it hasn't done anything like it since, and I have run CFS2 a lot since then.
So, Betterlife, if you haven't got your old drivers from your old Video board out of your computer or you have and it still is causing trouble, I suggest reinstalling the OS.
Granted I am not a computer engineer, but it worked

Wilder