I have to write a demo application for a customer and currently use free .net 3’d party trial library. If customer would be pleased with demo we will purchase commercial version for the project.
Meanwhile trial version occasionally throws “You are using trial limited functionality” message box that can ruin demonstration.
How would you personally block (close) such popups?
Actually, you should not attempt to do that, ie programatically overriding the behaviour of the 3rd party trial lib. If you are building a demo, your targeted customers should understand what a demo is and go along with this.
If it really is annoying, then contact the 3rd party vendor and ask for a time limited full version without the popping message boxes. In my experience, they are usually keen to helping you out in such matters.
EDIT
Theory aside, have a look at this article, might be easier than your no-interaction-win-service solution.