OK, first of all you're not allowed to talk about cracks/no-cd patches etc. etc.
Yes, it is true that you can backup your game CD so the game thinks it's the original... that's what this whole forum is about.
How to do it depends on the protection of the game. Use this to find out a protection for a game, and depending on what protection it is you use certain programs.
Take a look here, here and here.