Legal question regarding games...

[jlg6184]

Hello all, I am new to this board, and I am well aware of your rules, and I will abide by them. But I do have a question that I hope doesn't get misconstrued as a potencial "ban". I have been researching games for college (to make a compilation CD for the class). I have noticed that some games are completely available for free. They are considered abandonware. So my question is, so I don't get in trouble, how long does it take for a game to reach Public Domain status?

Note: I absolutely do not want to pirate games and take away from the makers, I am simply talking about the games that have been dropped by their makers and are issued as freeware and abandonware.