SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.
TreeSize Professional - TreeSize Professional is a robust Graphical Manager developed by JAM Software to help you perform different operations on your storage systems like analyzing the data, organizing and freeing up the storage system effectively, and viewing the usage.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Folder Size Catalog - Folder Size Catalog is a handy solution that offers a detailed view of your folders sizes to enable you to find the disk space distribution with great ease.
TreeSize - TreeSize tells you where precious disk space has gone to.
JDiskReport - JDiskReport enables you to understand how much space the files and directories consume on your disk...