A tool to determine what the disk is busy with?

Question

Hard disks

Hello! googled googled but never googled.
Tell me what tool should I use to find out what the disk is busy with, why it can't be formatted?
Personally, my guess is that I put the crooked Windows, BUT it's possible and everything is fine. I'm trying to format from the system, it says
I can't complete the format.
Format not a disk, but a partition on a disk that was once used by the system. At the moment, it has old system files and the partition is marked as system.

Answer 1

What the disk is busy with: WinDirStat ( download ).
Partitioning, formatting, maintenance:

1. Acronis Disk Manager
   
2. Paragon Hard Disk Manager
   
3. EASEUS Partition Master
   

Answer 2

Disk usage can be viewed in the Resource Monitor.
What is disk usage? It does nothing to prevent the completion of formatting.
If it cannot be formatted, then the drive is most likely defective.

Answer 3

As they said - starting with Windows Vista - the computer is not called "My Computer" like Windows XP and all previous ones, but simply "Computer" - because now it is not your computer, but a whist computer)))
https://technet.microsoft. com/ru-ru/sysinternals