Nice Tool - Analyze hard disk usage with Free WinDirStat Tool for Windows

WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows.
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.

 It cab be downloaded from the following url
http://windirstat.info/