I have seen hidden partitions on peoples computers that can be hiding various unwanted malware etc.
If you have multiple hard drives or partitions , look for restore partitions first ( don’t delete or format that) but the ones to look for are the ones that are a few megabytes in size.
So how do you find the partitions?
On your start menu , right click on computer and click on manage
This will open Computer Management
Click on Disk Management
You will then see all the various partitions on your computer
Remember be careful when doing this but it can highlight a problem area for you as many virus infections can manifest themselves into a small partition on your hard drive.
EaseUs have a free partition manager which will also show the partitions on your hard drive but remember if you dont know what you are doing leave it alone.