Hello, I'm trying to play Capsized coop, but the game only detects/recognizes the (hard)corded 360 controller, while the wireless 360 controller (connected with an USB-cable) goes unnoticed.

you need a receiver for that: http://www.alteredgamer.com/xbox-gear/11612-using-your-xbox-360-controller-on-your-pc/

I'd also like to add that after having completed the entire game with a wireless 360 pad, mouse and keyboard are far better.... It does feel a little unnatural to jump by pressing up, but the aiming is far better with the mouse. This is a really fantastic game, and I still fire it up from time to time so I can improve my stars on the levels.