My nVidia GeForce 8800GT had a serious problem with its stock cooling fan: it started to make strange noises and I later discovered that it was hitting the heat sink, because of an abnormal rotation that was causing the blades to go up and down. I couldn't find any way to fix it.
I bought a replacement cooling set (fan and heat sink) which I managed to mount on the card with no hassle at all. But I suddenly discovered that the power supply plug of the fan had two pins whereas the connector on the card had four pins. The fan plugs on the motherboard, instead, have 3 pins! I felt discouraged and started complaining about myself... :(
Fortunately (or not?) I discovered that on the MB there was an unused male plug to install an IEEE 1394 connector. It had 9 pins, and two of them were coupled and marked +12V and GND respectively. I distorted the pins in order to force the fan female plug to make contact with these two pins.
I started the system, and the fan worked. The GPU temperature is fine.
I'm not here advertising my bravery, but merely asking: how much is my machine at risk? Is this tricky workaround dangerous, or not?