mmh... only a suggestion. If you are going to have DVDs sold with it, hire a good lawyer and be sure to have no real estates at your name.
Your protection is illegal and the DVD reseller will be sued before or later, then they will sue you for damage.
You cannot:
1) install/run software on a computer without having the user to accept an EULA.
2) install a TSR equivalent without telling it to user.
3) make a reboot necessary (it might be an hospital computer, linked to heart-pumping stuff, you know -and for Murphy's Law, it will happen...)
For more references, goto Marc.Russianowich site and see the Sony's work (your one would not be really different in its principle, xcept coded better
)
Of course, if you need not to worry of legal side, there's no problem in it -it depends on what you wish to do with such protection.