Diskdeleter - Diskdeleter is data removal software that helps protect your privacy by securely deleting data from your hard drive.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
east-tec Eraser - Protect your sensitive data and privacy, and securely erase all evidence of your Internet and PC...
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.
Wiperapp - Software build to meet all needs of companies dealing with erasing data on daily basis.
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.