CD Drive problem

Hello,
I want to upgrade my friends old CD drive and I replace it with one of my other spare ones (that has been use in anther computer before) correctly, but then the computer doesn't show anything on the screen and I can't do anything. I just turn the computer on the CD drive light goes on but it just does nothing no screen can't open the cd drive can't do anything just hummmms away. What do I do? I need this fast please! thanks so much