Why do i receive, "The serial number has already been used and can be installed only once" when entering a Test Drive license?

As the error message suggests, a Test Drive license number can only be entered once per PC regardless of whether you uninstall or use a different version of VisualDSP++. This is also true for Evaluation licenses (sometimes referred to as EZ-Kit licenses). You may also receive this error message if you try to install a Test Drive license after you have installed an Evaluation license for the same architecture.