macandmobile

When formatting a FAT32 drive in MacOS X using Disk Utility, the queastion is whether to format for GUID or Master Boot Record (MBR).

If you’re looking to set up a disk for use on a Mac, then the short answer is to use a GUID Partition Table (GPT) disk

If you’re going to use these as Mac OS X boot disks or as local data disks, then you will want to use the GPT-partitioned disks.

If you’re planning to swap the disk with a Microsoft box or another platform, then you may want to use the older MBR format disk partitioning scheme.

From here.