Snow Leopard requires GUID if I remember correctly from an early upgrade that I had to do here at my school. The drive on a MacBook Pro had been formatted with Apple Partition Map instead so I had to use CarbonCopyCloner to clone, then reformat, then restore, then upgrade. Anyway I would stick with GUID. Chris On Feb 4, 2010, at 2:23 PM, Paul Moortgat wrote: > Is Guid to prefer in all situations internal and external for an Intel Mac to format? > I just received a 1T Hitachi drive to replace a 500 GB internal Seagate. > I think to make 2 partitions. One to copy the complete startup disk via SuperDuper, and the other half for daily use. > I can format the 1T internally or externally. > > Paul Moortgat > _______________________________________________ > X4U mailing list > X4U at listserver.themacintoshguy.com > http://listserver.themacintoshguy.com/mailman/listinfo/x4u > > Seven Cent Deals - Great legacy stuff Great Legacy Price > http://www.drbott.com/prod/db.lasso?cat=Seven+Cent+Deal