I had an old HDD with Windows 10 on C drive (let's call it Old Windows) and media files on D drive. I deleted 5GB of files from old D drive which would of course go into the hidden Recycle Bin folder of tthe old D drive.
Then I purchased a new HDD, connected it along with the old HDD and did a clean install in its C drive of Windows 10. When I'm logged into the new Windows, and go to the media partition of the old HDD (which is now called F drive instead of D, of course) and make 'protected system files' visible, the Recycle Bin doesn't show the files deleted when the Old Windows was active. The F drive showed 111 GB free. Then I went to the BIOS and activated the old HDD, logged into the old Windows 10 installation, and emptied the Recycle Bin there. Now when I'm back to the new Windows, I see the free space is 116GB in the F drive (old D drive).
But imagine if, without emptying the Recycle Bin of old Windows, I had to simply format the old HDD's C drive (which is called E drive now) from the new Windows 10 parition, how would I find the 5GB of files from F drive to delete? Where are they hidden in F drive?