If even xpadder doesn't recognize button presses, but the controller lights up, it may be a driver issue. Perhaps a windows update created compatibility issues or something? I know all my PC controllers, before discovering motionnjoy, came with install discs, though didn't need them.
If you don't have such a disc, you may be able to find drivers by googling the make and model.

If no luck, I'd say to test a different controller--it might just be dead inside. Like Lindsay Lohan. If you have a PS3, you can set up a controller with motioninjoy, which I honestly find even better than Logitech, despite some config quirks.