Hello all, I need to take a MacBook from Leopard to Snow Leopard as I need to load up a citrix app from the app store. Thereafter I'll probably wait until Mountain Lion shows up. Problem is, the upgrade needs a CD and the silly jap's-eye CD drive built into the mac doesn't work, usually no biggie as it's never used. So my question is, can I load up the new OS using an external USB CD drive or will this not work? Thanks!