Macbook keeps ejecting OSX install disks I have this 15 inch Macbook Pro (Mid 2007) with OSX Tiger 10.4.11.

I am trying to upgrade OSX to Snow Leopard (10.6) but all CDs and DVDs keep getting ejected without my doing anything.

How can I prevent this automatic ejection of install discs?
Often this happens when the disc needs cleaning. Soft cotton cloth, warm water, a little dishwashing liquid ... gently, gently ... rinse ... dry softly with aforementioned cloth, not in circular fashion but from center of disc towards outer edge, turning disc as you go.