It's called ccleaner and it will make drastic improvements in your computer speed. It cleans out old registry files from uninstalled programs, unused files, etc... that slow your computer down.
IMPORTANT!!! -- WHEN YOU RUN THE PROGRAM, THE BOTTOM SECTION OF CHECK-BOXES (NAMED "ADVANCED") ARE ALL UN-CHECKED. YOU NEED TO GO THROUGH AND CHECK THESE AS NEEDED - THIS IS WHERE YOU GAIN YOUR SPEED. I ONLY LEFT "MENU ORDER CACHE" AND "TRAY NOTIFICATIONS CACHE" UNCHECKED.
Hope this helps!!
www.ccleaner.com