WinDirStat, Windows Directory Statistics, has been around a long time and is still being updated. WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows. Some of us have used Spacemonger, which presents a treemap view of disk usage. Spacemonger’s biggest advantage over WinDirStat is that it is faster. Here are some advantages that WinDirStat has over Spacemonger:
Displays directories and files in a hierarchal list.
Easy analysis by file type – a pane lists them, and it will highlight all files of that type in the treemap view.
Color coding based on file type.
You can just only scan a folder (I have used subst with Spacemonger many times). [more]
I suggest you just try it out and start clicking on stuff. Be sure to check the configuration options (you will want to turn off the Pacman Animation).
The most recent version is packaged as an installer. However, I actually extracted the files and it runs fine.