Mac OS X Tip: Getting a disc out on startup
Sometimes when Mac OS X becomes unresponsive while writing to a disc or using a disc you can get the spinning beach ball and the disc will not eject. Don’t panic there is an easy way to get it out.
1. Hold down the power button until the computer shuts down
2. Hold down the mouse button while turning on the computer and keep holding it down until the disc ejects.
3. Let the computer boot normally
4. That’s it! You’re done, disc should be out 
Cheers