Clonezilla - Clonezilla is a suite of software that's designed to allow you to back-up and image new hard drives with your data.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
Macrium Reflect - Macrium Software - the creators of Macrium Reflect backup, imaging and cloning software.
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.
AOMEI Backupper - AOMEI Backupper is a software created to help a person backup, restore, clone, and sync their entire Windows system.
TreeSize - TreeSize tells you where precious disk space has gone to.