This behavior could be related to pv.exe that the Control Panel uses to kill processes but is not being released as it should.
When you notice this, simply check the Windows Task Manager - right click on the Task Bar and select Task Manager then the Processes tab - to see what process is using up resources.
If you see the pv.exe process using lots of resources, then try and kill the process - but as you say when you close the CP it kills what ever is causing the disk to be accessed anyway.
It is not any virus or malware activity from the CP but a slight malfunction perhaps.
You can download the latest version of the Control Panel from here:
and overwrite your existing CP with the new one.