Autoruns - See what programs are configured to startup automatically when your system boots and you login.
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.
TreeSize - TreeSize tells you where precious disk space has gone to.
Glary Utilities - The No. 1 Free, Powerful and All-in-one utility for cleaning 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.