There are very few power supplies that allow their fan speed to be controlled by the motherboard, and even fewer that allow software to modify their speed. Even if your power supply is one of these rare beasts, you would not be able to shut off the fan using either of these methods. Even if you were able to shut it off using one of these methods, the fan would still spin up when first started since the system wouldn't have been able to give it the instruction to stop the fan yet. Given this information, I have no doubt that the failure of the power supply fan has everything to do with you plugging a device into it while running and has nothing to do with your tinkering around with the settings for your video card.
The biggest piece of conclussive evidence is the fact that the fan that was connected to the power supply also stopped working. This fan didn't stop working because the fan was fried (since it worked when you plugged it into a different plug); rather, it wasn't working because that power supply connection wasn't receiving a current anymore. The only reasons a power supply connection would totally cease supplying a current is that one or more of the wires became damaged (which doesn't seem to be the case here), the power supply is off (not the case), or the current-supplying circuitry became damaged (which can happen when you connect/disconnect devices while the power supply is in operation).
As much as I would like to give you a ray of hope for your power supply, I have no reason to believe that your power supply is not damaged. As I stated before, you could try to make some fixes to it so the fan works again, but this would degrade the reliability of the power supply since you will be changing the way it normally works and run the risk of damaging the unit further.