Description: MBR (Master Boot Record) controls the startup process of operating systems on a hard drive. For many years Hard Drives have used a small section at the beginning of the hard drive called the Master Boot Record to hold the information about the hard drive and how it is divided. Using this system a hard drive can be divided into up to 4 primary partitions or 3 primary and 1 extended partition (that can contain up to 128 Logical partitions / volumes inside that extended partition. Note that a logical partition looks and acts exactly the same to the operating system as a primary partition). The MBR reads information from the BIOS to know the size and geometry of the hard drive. It is being replaced - especially with hard drives over 2 TB, by the GPT - G(lobally Unique Identifier) Partition Table.

MBR is supported by all versions of Windows and Linux. Mac OS X uses the GPT. Windows server 2003 SP 1, Win XP 64 Bit, Vista and Windows 7 all support GPT as do most modern Linux distributions.

The diskpart command can be used to reset the MBR on a hard drive in the following way:

• Boot into the Windows installation Disk
• Once on the install screen during the installation, press Shift+F10 to get a command prompt
• Type in diskpart then hit enter
• Type in list disk then hit enter
• The Disk Drives should now be listed, make sure you note which disk will be cleaned.
• Type in select disk x (where x is the number of selected disk) then hit enter
• Type in clean then hit enter
• The screen will return the message DiskPart succeeded in cleaning the disk.

The process is now finished and an operating system can be installed on the drive or a new partition table written.