Assasin's Creed

[Emayan]

I bought the game, completed the installation, did everything right, everything went okay and I didn't have a single trouble.

But when I tried to play the game it keeps telling me to "insert the CD ROM and click OK to restart the application".

I tried using the game CD but it doesn't work. How do I play the game? Please help me!.

P.S: I'm not very good with computers (You might have already guessed that ) so please explain the process in layman's terms.