Assuming you have dumped temp files (including all browsers you have installed) and cleaned out the download folders, there isn’t a whole lot else to do beyond uninstalling apps and moving data to a different location (external storage of some kind).
Every time Windows installs updates it keeps a kind of mirror of each update in a folder so it consumes more and more space. You can’t clean out this side-by-side folder or it will break the OS.
You could do a format and reinstall of a current rev and that will dump the folder, but it’s only a temporary fix. Not to mention you have to back up all of your data and reinstall all of your apps.
If it’s not a laptop, add a huge second HD and move as much data as you can to it.
The other option is to buy a new, larger drive and replace it.
Good luck.