The GUID Partition Table (GPT) was introduced as part of the Extensible Firmware Interface (EFI) initiative. GPT provides a more flexible mechanism for partitioning disks than the older Master Boot Record (MBR) partitioning scheme. Drives based on the MBR (Master Boot Record) have a limit of four Primary Partitions. The number of partitions on a GPT disk is not constrained by temporary schemes such as container partitions as defined by the MBR Extended Boot Record (EBR).
The GUID Partition Table (GPT) can be implemented under Microsoft Windows XP x64 edition, Windows Server 2003 (64-bit), Windows Server 2003 SP1 (all versions), and the Windows Vista and Windows Server 2008 operating systems.