Differences between MBR and GPT

MBR (Master Boot record)

• use LBA (logical Block Address) 32bit addressing
• support up to (2^32 x 512 = 2.19Tb using 512byte sectors
• support 4 primary partition table

GPT (Guid Partition Table)

• support more than 2Tb
• use UEFI (Unified Extensible Firmware Interface)
• support up to (2^64 x 512 = 9.4Zb) (Microsoft OS support up to 256Tb)
• support 128 primary partition table
• provides redundancy by writing the GPT header and partition table at the beginning of the disk and also at the end of the disk.

Notes

• 32-bit Microsoft Windows™ will not provide bootable disk support for GPT, only 64-bit OS has support. Need machine that support UEFI BIOS.
• For MS Windows, both 32bit/64bit can support GPT Data Storage support
• For XP, 32bit cannot support both boot/data disk, 64bit support data disk only.
• For Windows 2003, all can support data disk only.
• For Windows 2000,NT, W98, W95, cannot support data/boot disk

http://msdn.microsoft.com/en-us/library/windows/hardware/gg463525.aspx#GPT1