CCleaner

CCleaner is a utility that allows you to optimize and clean your computer. It lets you manage programs, edit startup items and clean all areas in your computer.

Some of its functions:

• Registry Cleaner
• Uninstaller
• Startup Items Editor
• System Restore Manager
• Drive Wiper
• Internet Cookies Manager

Download: Download for Windows

Now available for Mac - http://www.piriform.com/mac/ccleaner
Download for Mac