MBR = Master Boot Record is the standard partitioning scheme that’s been used on hard disks since the PC first came out. It supports 4 primary partitions per hard drive, and a maximum partition size of 2TB.
GPT = GUID Partition Table disks are new, and are readable only by Windows Server 2003 SP1, Windows Vista (all versions), and Windows XP x64 Edition. The GPT disk itself can support a volume up to 2^64 blocks in length. (For 512-byte blocks, this is 9.44 ZB – zettabytes. 1 ZB is 1 billion terabytes). It can also support theoretically unlimited partitions.
Windows restricts these limits further to 256 TB for a single partition (NTFS limit), and 128 partitions.
Also, there are a few things to note about marking a partition as active:
A logical drive or extended partition cannot be marked as active, only primary partitions can be changed to active.
You can only have one active partition per physical hard disk. Doing otherwise will cause all kinds of problems.
If you have several physical hard disks on your computer, you can mark a partition as active on each disk, but only the active partition on the first hard disk detected by your BIOS will start up the computer. You can go into the BIOS and change the order to detect hard disks.
Basic Disk Storage
Basic storage uses normal partition tables supported by MS-DOS, Microsoft Windows 95, Microsoft Windows 98, Microsoft Windows Millennium Edition (Me), Microsoft Windows NT, Microsoft Windows 2000, Windows Server 2003 and Windows XP. A disk initialized for basic storage is called a basic disk. A basic disk contains basic volumes, such as primary partitions, extended partitions, and logical drives. Additionally, basic volumes include multidisk volumes that are created by using Windows NT 4.0 or earlier, such as volume sets, stripe sets, mirror sets, and stripe sets with parity. Windows XP does not support these multidisk basic volumes. Any volume sets, stripe sets, mirror sets, or stripe sets with parity must be backed up and deleted or converted to dynamic disks before you install Windows XP Professional.
Dynamic Disk Storage
Dynamic storage is supported in Windows XP Professional, Windows 2000 and Windows Server 2003. A disk initialized for dynamic storage is called a dynamic disk. A dynamic disk contains dynamic volumes, such as simple volumes, spanned volumes, striped volumes, mirrored volumes, and RAID-5 volumes. With dynamic storage, you can perform disk and volume management without the need to restart Windows.