My computer crashes, when I play Oblivion

I get this error report (translated from Danish) An error ocurred and windows has been shut down to prevent the computer from being damaged. DRIVER_IRQL_NOT_LESS_OR_EQUAL
If this is the first time you see this stop error, then you have to restart your computer. If the screen is shown again, then you have to do the following: Make sure that all new hardware or sofware is corrected installed. If this is a new installation, if you have ask the hardware or software manufacturer if there are any Windows updates, that you might possibly need.
If the problem occures again, then you have to deactivate or remove hardware or software recently installed. Deactivate some settings for the BIOS memory, like chaching or shading.
Technical information:
*** STOP: 0x000000D1 (0xFFFFFFFF, 0x00000006, 0x00000000, 0xB9874705)
*** portcls.sys - Address B9874705 base at B9873000, DateStamp 41107f13

My computer is homebuild. It is brand new. It was built this saturday. I believe I have all the the newest patches. I might be missing the newest driver for my motherboard, but I can't seem to find any. I used the one on the cd. It always happens when I play Elder Scrolls 4: Oblivion. I haven't any other games, so I don't know if it occures doing other games.
Specs:
Core 2 duo E6600
2 x 1 gb Corsair 800 mhz ram
7950 gx2
Asus P5N32-SLI/SE/Deluxe
Enermax EG 565AX-VE /535 Watt/Dual Fan

This is a tough error because it could be a hardware related problem or a legit windows driver error since portcls.sys is a system driver for the PCI and DMA.

If you have installed the latest driver pack for your mobo and all devices (in particular the sound card) and tried the manufacturer driver over the MS default driver then it would not hurt to get The Ultimate Boot CD and get memtest running for several hours. For cpu / system stress test I prefer to boot up knoppix since you can run multiple instances of prime95 and surf the net (if your network is detected properly).

it looks like you have a slight problem in there ...first of all before jumping into games i recommend to you to run a simple component check:
- check the memory for errors or other problems ...with memtest..run it for at least one time ..untill it reaches 100%
-check the video card ..with a simple 3dmark2001 in looping ....and leave the test for at least one hour..see if you have problems with temperatures ... check the temperatures of the video gpu and also the temperature of the psu.....watch for restarts also..
- you can also run and loop the aquamark test and maybe prime 95...

you may say these tests are old .. but they are pretty accurate...for instance if you have a problem with the memory (blue screens, unexpected interrupt of the programs, restarts, etc) memtest will tell you exactly wheter you should exclude the memory module from your black list or not.....3dmark2001 although is pretty old it uses resources from cpu and gpu and thus it tests the stablility of your new sistem ..if you run it long enough......

i think for now the psu is out of the question ..the problems related are ..restarts...expecially in power hungry app like games ..
i also recommend an bios update....
good luck

Yes ubcd and knoppix are both bootable, they are cd "images" that needs to be extracted to cd with "burn cd from image" option in nero or use something like cdburnerxp. Since you found a problem in memtest - that should be resolved first.
Have you tried one stick at a time to see which one is bad? If both maybe check your BIOS timings and see if they match the memory specs.

you say you have a mem error...that`s bad .....
try to reinstall the modules .... change the memory banks..reset the bios....change the SPD....