Hello. This is my first post on any forum... I've always just read them, but I need specific help this time! I have a 1st generation 13" white macbook with 2gb of ram and a 2ghz processor. I upgraded my internal hard drive to a 500 gb hard drive, and when I did that - for some reason, the default partitioning table was an apple partition. Now that I'm trying to install Snow Leopard, it says I need a guid partitioning table. I've cloned everything to an external drive, and I'm ready to reformat the partition table of my internal hdd to guid, but disk utility can't unmount the disk. I'm kinda stumped, and I can't find any forums that are specific enough to help me, so... here I am. Thanks for any help - it's deeply appreciated.