I'm sending my 13" MBP in to Apple to have a minor mechanical issue repaired and so I'm installing a fresh copy of 10.5 just for security reasons. Yeah I know... paranoid maybe, but whatever. I have a time machine backup so it's really no sweat off my back. In any case, I thought I'd just use my retail 10.5 disc, but it gave me a bunch of grief. When the computer would boot up with the disc it would just go to a gray screen and sit there. You'd hear the CD spin up and then stop and it just sat at the gray screen. I tried holding down 'option' before the full boot and it found the CD, but when you clicked it it would just freeze. I just put in the Leopard install disc that came with the computer and it's installing just fine. Any ideas? I guess I'm not too worried since I have the disc that came with the computer and I'll be getting Snow Leopard as well, but it'd be nice to know my retail 10.5 disc would work regardless.