None of my 4 present internal drives are formatted in Guid. One has a system 10.5.8 and I intend to keep it for a long time. I backup to a non Guid external drive which I can use as a startup for the Mac Pro. Paul Moortgat On 04 Feb 2010, at 22:30, Chris Long wrote: > 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