This computer is super slow and I'm trying to speed it up, so I want to reinstall OS X. I've tried many different things with the install disk. The stupid thing doesn't even work half the time. I tried it the first time and the screen turned gray with a broken in half Mac symbol in the middle with an old version of the spinning beach ball in the corner. I couldn't move it. Sometimes the disk thing comes back out, as if the disk is scratched. It isn't. I just can't get it to work. Yes, I tried restarting and holding c, as well as making the disk the start-up thing. How can I do this?