I say 90% because if you're using some no-name cheapo controller you got at a yard sale / strange imported gamepad, it might have it's own weird drivers that need installing. Other than that, you should generally be good to go.
That said, many controllers need their own software installed if you want to do advanced stuff like setting up custom profiles for particular games, etc. But it seems like for what you want to do plug-n-play plud using the windows control panel--->game controllers should suffice. Good luck!