I started playing Portal 2 on my friend's Steam account on his Mac, and just bought the game for myself to play on my PC. Is there a way to transfer the saved game from his account on his Mac to my account on my machine?
Save games reside in:
You should be able to copy them from one machine to another without problems, but be ware that Steam cloud synchronization might interfere with your copy process. So be sure Steam Cloud is done with syncing.