CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Wise Disk Cleaner - Clean junks of Browsers, remove junk and useless files of Windows and Defragment your disk. Wise Disk Cleaner can delete these unnecessary files on your hard disk to free up disk space and make your computer run faster.
TreeSize - TreeSize tells you where precious disk space has gone to.
CleanMyPC - A smart cleaning tool for a better-running computer.
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.