All primary partitions will be imaged first while logical drives are assigned according to subsequent letters.
And it must lie in the hard disk accessed by computer when OS is booting.
There should be only one active system partition in one disk.

Several basic disks are allowed to exist on computer, each of which has its own active partition.
However, you’re free to start computer only by one specified disk.
This active partition will become activesimple volumeafter disk conversion.
Then, it will become inactive.
Actually, active partition is the primary partition with boot data.
It can achieve taking over starting tasks and other operations from BIOS for boot system.
it’s possible for you to generally divide a 10G primary partition in a small hard disk.
You dont need to divide a primary partition that is too large.