I have a 15" Macbook Pro running OS X 10.6.8 and it gets stuck on the blue screen when trying to boot. It will boot in safe mode. I've tried to reinstall the OS but it says to clean the disc and try again. I have two OS discs and one looked scratched but one is clean and perfect. It reads other discs (it let me install iLife). When it tries to reinstall the operating system it makes a loud clicking noise, but it doesn't do that with other discs. I've tried verifying and it didn't fix it. I'm so frustrated.