I recently cleaned up an old "7" computer and got rid of over 40 gigabytes of junk in the windows update folder alone. It also had a windows old folder since the OS had been reinstalled. I don't remember how large it was, but it was a biggie.

Open disk cleanup, click on clean system files. Put a checkmark by everything on the list. Especially "windows update cleanup" and " Windows old" if you have it. You'll have to scroll down to see all of the list. Now look at your hard drive properties. It will look a lot better.

P.S. I know  this will work on 7,8, and 10. Will probably work on XP and Vista.