the 100% method would be a complete OS install with formatting.
You may never discover every little piece, the software developer does this on purpose.
Most all software hides a little bit away somewhere where you can't find it. This is used as a time clock so it knows your history with the software. It tells when your trial version has run out and will not let you install it a second time. An old trick for outsmarting this was set your computer clock back ( stay off the internet)
As far as I've noticed having the other versions installed should never cause any issues. A new interface should make no difference and your just as likely to get that message with X2 if the drivers are not correct.