Not really sure if my suuggestion will be effectif. But in my experience, I found the best way to remove the NAV is to insert the NAV CD in the player, and double click on "Set-Up", (As if I'm making a new install), but choosing the option "Uninstall" there when it pops up.
If not having a CD, Double click on "Set-Up", and doing the same thing.
Anyway, techies are there to help when they get here as you know.