The Freeware and Open Source Software Thread

[Xiahou]

WinDirStat
Open Source: Yes

WinDirStat is a disk usage statistics viewer and cleanup tool for Microsoft Windows (all current variants).
WinDirStat 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.

I got tired of poking around on my games drive trying to find out where all the space has gone- so I downloaded this. I fell in love instantly when it showed me several gigs worth of temporary patch files buried deep in a games install directory.

Here's a sample image of how it displays drive info:

Spoiler Alert, click show to read: 

The individual blocks represent files- the size of the block indicates its relative size. Directories are color coded.