Hi there! I have some questions on which Snow Leopard I should buy. My bro and I have macs. He has a 24" iMac running Tiger while I have the 13" Unibody Macbook running Leopard. We're thinking of buying the Family pack... Since my bro has Tiger, he is going to need the Box set. If he bought the box set, can I use the disc to install snow leopard on my macbook? Or Do I have to buy the upgrade disc? Thanks!