A. The Master Boot Record (MBR) format can support partitions as large as 2TB. However, the GUID partition table (GPT) disk type can support partitions far larger than 2TB and support as many as 128 primary partitions. The MBR format can support only four.

Windows Server 2003 (both 32-bit and 64-bit) and Windows 2003 x64 Editions support only GPT partitions as a data volume. Itanium computers support GPT for both boot and data volumes. Windows Vista and Windows Server 2008 (both 32-bit and 64-bit) support GPT disks with Extensible Firmware Interface (EFI)-based systems capable of booting from an EFI volume. Windows 2000 and prior Windows' versions won’t recognize GPT disks.

Microsoft has a GPT FAQ at Windows and GPT FAQ.