I bought Mafia II on eBay, the Steam version. Not a Steam Key, but the whole game, all files included, but I was told that I need Steam to play it.
I tried adding the game to my Steam library, but it won't play. I also tried executing the game directly but still no success. It just creates a file called "mafia2.exe.4936.STEAMSTART" (the number is always different) in the same folder but doesn't do anything beyond that.
I have a good computer with all the latest stuff installed, and I'm able to run all my other games no problem.
Is there a certain procedure I need to undergo to add a Steam game, or something I could do to get this game to work?