Change nvidia gpu shutdown temperature?
 

I've got a minor problem with my GPU: I replaced the OEM GeForce 6200 with a 9600 GT, but I believe the shutdown temperature is still set to the 6200's; causing annoyance with graphically intensive programs/games. It was a fairly small card, and has a low shutdown temp. BIOS revealed no settings, is there a setting for this in slack?

I have seen many cards, but never one that had a settable shutdown temperature. The NVidia 9600 GT will clock down if it reaches a temperature that is too high (normally 105°C, dependend on manufacturer and card) to cool down.
But seriously, if you have temperature issues with your card, setting a shutdown temperature would be rather pointless. You should improve your systems cooling, maybe with adding a case-fan or two.

Yeah, this is not a solution. Instead, clean dust, add more case fans, etc.

With the proprietary Nvidia blob, you can also use Coolbits to get the fan speed onto nvidia-settings, for some cards. See nvidia readme.txt. Then you can crank up the fan speed as needed. But if you are running hot inside the case, more fans are the key. Besides the power supply fans, I have 3 additional: 1 intake with dust filter, 2 exhaust. User gkrellm or conky to monitor you temps and see if that is the issue.