CCleaner - CCleaner cleans, speeds up and frees up space on business endpoints.
Registry Workshop - Registry Workshop is an advanced registry editor.
Wise Registry Cleaner - Registry Cleaner and Optimizer.
RegCool - RegCool is an advanced registry editor.
Glary Utilities - The No. 1 Free, Powerful and All-in-one utility for cleaning your PC
Regedit - The Microsoft Registry Editor (regedit.