The first and easiest thing I would do is make sure your hardware is all intact and connected properly. I'm assuming it is, however sometimes it helps...IDK why.
Second: what is your rig? I doubt that you are overloading your new psu, but too many hd's and LOTS of hardware does eat up power. It would help to know what you had before the new installation of the gpu and powersupply (for comparison)
Third: open the nvidia control panel and check the gpu temps before running the game and (if at all possible) during ANOTHER game that won't crash your system.
Fourth: You might want to install a gpu tuner such as Atitool (that works with nvidia, so no probs there) since it has the capability to scan for artifacts.
Fifth: did you install the drivers from the cd? or the updated ones off of Nvidia? I never use the drivers on teh cd because usually they are dated and I can get the latest even though i'm running basic xp drivers.
Fifth and 1/2: try uninstalling the drivers and reinstalling the latest ones.
My gut feeling is that none of these things will help 🙁
I hate to say this, but there might be something physically wrong with either the psu or gpu. I highly doubt it.
If the hardware is the case, try borrowing a friends pc and run your 9600gt in it, try your old card in your rig with and without the new psu, and try the psu in the friends pc if possible. That can help diagnose the problem.
I hope I was of some help...