so i got my first Mac today and it didn't come with snow leopard installed but it did come with a snow leopard disc. the problem is whenever i try to upgrade, i insert the disc, it stay's in for about 30 seconds making weird noises, and then it spits the disc back out. i'm very new to mac, today is my first time ever using one so i really don't know what to do so i came here. i have a 13 inch MacBook Pro running on OS 10.5.8. also, i installed iWork perfectly fine so i'm guessing it has to do with the disc.