Active Partition Problem in Windows 7

If you have accidentally changed the active partition of your system and thereby unable to boot your OS, then follow the below technique to change back your active partition to the original settings.

Run the repair console by tapping F8 key during bootup. If you cannot access the Repair console, then You will need the System Repair Disk to use Diskpart commands to mark the Windows 7 active partition.

After running the Repair Console/System Repair Disk, open the DOS Command Prompt and use the following commands to set the active partition:

DISKPART

LIST DISK

SELECT DISK # (# for Windows 7 disk)

LIST PARTITION

SELECT PARTITION # (# for Windows 7 partition, or 100mb system Reserved partition if you have it)

ACTIVE

EXIT