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 master boot record (MBR) disks, marks the system partition or boot partition with focus as inactive.
Your computer might not start without an active partition. Do not mark a system or boot partition as inactive unless you are an experienced user with a thorough understanding of the Windows family of operating systems.
If you are unable to start your computer after marking the system or boot partition as inactive, insert the Windows Setup CD in the CD-ROM drive, restart the computer, and then repair the partition using the fixmbr and fixboot commands in the Recovery Console.
After you mark the system partition or boot partition as inactive, your computer starts from the next option specified in the BIOS, such as the CD-ROM drive or a Pre-Boot eXecution Environment (PXE).
An active system or boot partition must be selected for this operation to succeed. Use the select partition command to select the active partition and shift the focus to it.