Howdy Fellow Grindean! I just so happen to of seen your post in the "Introductions Posts" and happen to know the answer! To my knowledge, in order for you and your best-est Pal to Co-oP together either A). You both need to have Full Copies and run the same version (Stable or UN-Stable) OR B).You both can Co-oP on the Demo Version of the game! Believe it!