http://windirstat.info/

http://windirstat.info/

WinDirStat is free software published under the GNU General Public License.

It is known to run on Windows 95 (IE5), Windows 98 SE, Windows ME, Windows NT4 (SP5), Windows 2000, Windows XP, Windows Server 2003, Windows Vista, and Windows 7.

WinDirStat is a disk usage statistics viewer and cleanup tool for various versions of Microsoft Windows.
Note: if you are looking for an alternative for Linux, you are looking for KDirStat (apt-get install kdirstat on Debian-derivatives) and for MacOS X it would be Disk Inventory X.

Please visit the WinDirStat blog for more up-to-date information about the program.

On start up, it reads the whole directory tree once and then presents it in three useful views:

• The directory list, which resembles the tree view of the Windows Explorer but is sorted by file/subtree size,
• The treemap, which shows the whole contents of the directory tree straight away,
• The extension list, which serves as a legend and shows statistics about the file types.