Just as regular exercise is good for your health, a regular workout for your hard disk is recommended. Windows has its own tools for doing this, but CCleaner makes a slightly better job of it.
The application is free to use and shows the door to all kinds of temporary files, from temporary internet files to old automatic back-ups from application such as Office XP and file sharing software. It also shakes out old entries from your computer's registry, such as unistallers and invalid shortcuts. The makers guarantee that it contains no apyware or adware.
CCleaner is one of the more popular system cleansing and optimisation tools available.
Note that this is the final stable CCleaner for Mac.