When your computer gets infected by a virus or worm, the virus often schedule itself to be run automatically when you start your operating system; some of them even register themselves to be run when any other application is started. Removing of it is not as simple as deleting it - after deleting the worm file, your operating system might not be able to start your applications (such as Explorer) any more. In order to properly remove the worm from your computer, it is often necessary to make additional fixes in your system registry, delete the links from your Startup Folder etc.
Here the avast! Virus Cleaner comes - it will find and remove selected worms from your computer, as well as fix the registry and startup items to make sure your system will work correctly after the disinfection.
Many worms - when activated - create additional working files on your hard disk. Even though these files alone are harmless, they are useless and they should not be there. When avast! Virus Cleaner detects and removes a known worm from your computer, its working/temporary files are removed as well. The same applies for worm-specific registry entries etc. avast! Virus Cleaner can also deactivate the virus present in memory. There is no need to start the tool from a Safe Mode - just start it and it will take care of the rest!