When I turn on my computer, it gets to the grey screen with the apple logo and a spinny thing to indicate that its busy. However, it hangs here interminably. Once, it got past this screen and just displayed a blue screen with nothing on it. I should note that the last thing that happened to my computer was that it froze, and I restarted. any thoughts? I can't boot from a cd because it won't eject the one thats in there, even holding the mouse button at startup.