I'm not sure if it was put in place for 360 players, but if you have a console copy of Portal 2, you should be able to sign up to the Steam Cloud via your console (provided you have a Steam account on PC). In doing so, you can then d/l a free copy of Portal 2 thru Steam onto your PC and play via PC.
I have Portal 2 but I've got it for PS3. It would have been fun to play with you Campion but I haven't set my PC d/l up either. Sorry about that.
Just as a side note, anoyone who DOES have Portal 2 should check out the new dlc for it. It's free and it's a continuation of the co-op story (so I've been told). Go grab it now if you haven't done so already!