Xinorbis is a comprehensive hard drive analyser that will show you, in detail, exactly where all your hard drive space has gone.
First you must tell the program exactly what you'd like to check (a folder tree, or an entire drive).
Then you must leave Xinorbis to do its scanning work. By definition it needs to scan every single file in your specified locations, so this will probably take a while. It's worth the wait, though, because when the process is complete you'll get detailed reports on every aspect of your hard drive use.
So you can see which folders are consuming the most drive space, for instance. Or which file types are proving to be particular resource hogs: movies, audio files, documents, images, whatever it might be on your system.
A "File Attributes" panel tells you how many of the browsed files are hidden (maybe useful for security), system files, created, accessed or modified today.
If others use this PC then you'll be able to sort your reports by file owner, so you can see which user is responsible for the most junk.
It's possible to search for files by date range, so you could (for instance) see how many files were created in the last month, and where they were on your hard drive.
A handy Folder History option allows you to compare the contents of a folder or drive over time. A Duplicate File Finder tracks down files that may be wasting your hard drive space right now. And you can create detailed reports on all of this, exporting them in HTML, CSV or HTML formats.