Since the McAfee Uninstall tool is not developed for McAfee VirusScan, I suggest you uninstall the application using Add or Remove Programs feature:
If you use Windows XP or bellow you can go to Start > Control Panel > Add or Remove Programs. In the Currently installed programs box, click on the antivirus and then click Remove.
If you have Windows Vista or above you need to go to Start > Control Panel > Programs > Programs and Features. Select the application and click on Uninstall.
If this doesn't work, you can try using Revo Uninstaller. Even if it can't uninstall the application normally, it will force it to uninstall by wiping out all traces of its presence from the system.
