Directory Opus is a popular file manager program, originally written for the Amiga computer system in the early to mid-1990s.

WizTree gives you more control over how you see your files, in addition to letting you learn more about them from one look.

Bitser is free Windows software for managing archives and backups. It supports ZIP, 7Z, RAR, ISO, MSI, VHD, GZIP, BZIP2,TAR, LZMA, LZMA2,etc.

XYplorer is a file manager and Explorer replacement for Windows. It's fast, powerful, portable, dual paned, and multi-tabbed.

Folder Size is a freeware disk size analysis tool that will display the directory sizes and folder tree sizes.