WinDirStat (Windows Directory Statistics) is a disk usage statistics viewer and cleanup tool for Windows. On start up, WinDirStat reads the whole directory tree once and then presents it in three useful views. The official download location and collaboration platform for WinDirStat has moved to GitHub:
https://github.com/windirstat/windirstat
Downloads and source code provided on SourceForge may not always be up to date. They are primarily used for disaster recovery purposes.