You probably uninstalled the entry named Malwarebytes Windows Firewall Control. Uninstalling Malwarebytes Premium does not uninstall WFC. The error that is: The path is not of a legal form. 1. Do you try to execute WFC installer from a mounted drive? 2. Do you use any installation parameter ? 3. Is this in a VM or your machine ? 4. Do you have Malwarebytes Premium installed also ?