If you performed a full install you can play without the CD in your drive by tricking the game. The copy protection will only check for the presence of a CD drive and the presence of a certain file. Set up a virtual CD drive using a tool of your choice and make sure it has the following file in its file tree:
Wine users can use Wine's winecfg program to set up a folder as a CD drive. Using cracks is not recommended since they can break compatibility with mods.