Partitioning: Marking a partition as active on a basic disk means that the computer will use the loader (an operating system tool) on that partition to start the operating system. The primary partition can be made bootable, by marking partition as active. The extended partition can not be marked as active partition.
Steps to mark partition as active in Windows 10
1. Press shortcut key WIN+R to open RUN box, type "diskmgmt.msc", or Right-click the bottom-left corner (or Start button) on the desktop to open Quick Access Menu, and then choose Disk Management.
2. Right-click on the partition you want to set active, choose Mark partition as active. The screenshot of "Disk Management" is shown below