I just bought a steelseries 3gc controller for my pc version of skyrim and cannot get it to work. Does skyrim allow the use of just plain old PC controllers or does it need an xbox controller? I would be thankful for any input or suggestions.

It uses 360 controller, google motionjoy, use it to emulate the 360 controller. It's how I play using my ps3controller.

Is MotionInJoy required with the 360 controller or just with the PS3?

Motionjoy or any other emulator isn't needed for the 360 controller. Like many PC games that support gamepad, the 360 controller in Skyrim has native Xinput support. Just plug it in, turn it on, and it is supported natively with all buttons mapped as they would be on the 360 version of the game. For wireless 360 controllers you need the wireless receiver/adapter.