I've never had any game detect a crack but one thing to be aware of is that there are cracks that extract your serial code and send it to the crack author, so make sure you're careful.Sorry. I completely forgot the question.
Using a program to make an image of the disk and then mounting it with DaemonTools or Alcohol120 is a bit safer than using an unknown crack. Some games detect the crack as a hack and will ban you for it.