Updated: April 17, 2012
Applies To: Windows Vista, Windows Server 2008, Windows 7, Windows Server 2008 R2, Windows Server 2012 R2, Windows Server 2012, Windows 8
On basic disks, marks the partition with focus as active.
DiskPart verifies only that the partition is capable of containing the operating system startup files. DiskPart does not check the contents of the partition. If you mistakenly mark a partition as active and it does not contain the operating system startup files, your computer might not start.
This informs the basic input/output system (BIOS) or Extensible Firmware Interface (EFI) that the partition or volume is a valid system partition or system volume.
Only partitions can be marked as active.
A partition must be selected for this operation to succeed. Use the select partition command to select a partition and shift the focus to it.