Recently I received this query from one of my readers who wanted to know how we can mark one of the hard disk partitions as Inactive or in other terms how we can unmark an Active partition. For all those who don’t know much about the Hard Disk partitions then we will go through the terminology briefly here.
Every hard disk has some partitions and if you access your Disk Management (via diskmgmt.msc) you can see all the disks and the partitions they have in your system. In the screenshot below, you can see that my system have one disk connected and some partitions as you can see. One of these partitions is marked as Active (highlighted in the box). This is the partition which is used to load the OS.
Actually every Active partition on the hard disk contains MBR (Master Boot Record) which is used to boot the OS. Every disk has only one partition flagged as Active. When the computer starts, it will read the MBR and determine the partition that is flagged as active. So this partition is invisible to all and also inaccessible. So in case you have mistakenly marked a partition as Active, here is how to mark it back as Inactive.
1. Open the Command Prompt by typing cmd in the Run box.
2. Now type diskpart which will open a new window.
3. Type list disk, this will lists all the disks connected
4. Now type select disk # (same as listed in the window), to select the disk where the partition is marked active.
5. Type list partition, this will display the entire partition list.
6. Now you need to type select partition # (same as listed) to select the partition to mark it as inactive.
7. Now just type inactive.
After you have done all the steps, the disk partition will now be turned back as inactive, and you can exit the session. Make sure you now select the right partition as Active, as your computer needs the boot loader to boot next time. [via]