Computer won't start after updating

I recently tried to updated my 2006 Mac Mini with Snow Leopard 10.6 and a screen popped up saying there was an issue and that the computer needed to restart. When it restarted the screen was a white loading screen with an apple, but now it won't move from that screen. I also can't get the disc out of the computer because it won't go to the desktop screen. I don't know what to do or how to fix it.