I have a 2.16 ghz imac that has worked flawlessly for me for 3 years, I finally upgraded to snow leopard and the system crashed during install. Now I have a screen that just has lines showing up and going away and then the system freezes. If I boot into safe mode everything seems normal. Also the disc drive will no longer read a disc. All of this started with the snow leopard upgrade. Any ideas? I am falling into a deep depression. Thanks.