This could be an example of having a wealth of HD space which soon becomes cluttered unless you do some regular housekeeping.
Certainly use the recommended sweeps for dead applications and "orphaned" files.
Most of these "Cleaner" applications verge on the over-safe side, to avoid getting a bad name for ruining your system.
Then only you, can search for long forgotten notes, documents, pictures and downloads. Also "image" files set up when burning CDs and not needed again.
If you have enough space, make a new folder called Junk or Dead, and move any unknown or long forgotten stuff in there, as a safeguard until you're sure it is not needed and then make sure you delete this as well. This is your version of the Bin, but safer since you need to empty the bin farely often and most of the Cleaner apps will do this anyway