What is CCleaner?
CCleaner is a system optimization/cleaning tool. It removes unused files from your system, allowing Windows to run faster and freeing up valuable hard disk space. It can also clear your internet history and act as a fully featured registry cleaner. CCleaner is fast (normally taking less than a second to run) and contains NO spyware or adware!
The software tries to install Avast too - Spyware, runs in background and collects information to send to Avast. Background mode can be disabled, but gets re-enabled on each run - Shows pop-up system wide ads from time to time