CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.
RegCool - RegCool is an advanced registry editor.
BleachBit - When your computer is getting full, BleachBit quickly frees disk space.
Registry Workshop - Registry Workshop is an advanced registry editor.
AVG PC TuneUp - Peak performance for your PC. Keeps it going for longer. - More Speed Turbo Mode
Regedit - The Microsoft Registry Editor (regedit.