WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.

CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.

WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.

Advanced System Optemizer - Clean, optimize and personalize your PC

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.

WinZip System Utilities Suite - Top-rated PC utility software to clean, update, maintain and protect your PC for good. Free Download for Windows and Mac.