The first part just means make sure VirusScan is up to date before running it. Right-click and check for updates just in case.
Sometimers infections can be trapped in System Restore where they are protected by Windows and disabling it temporarily will delete the infection along with any other restore files and folders of course.
If all this doesn't work then download, install and update the free version of this tool. Run it and let it remove anything it finds, reboot immediately if asked to.