My wife's computer has NAV Corporate on it. Same file, too, svkp.sys, installed four days after it was installed on *my* computer, back in 2004...when I installed TweakXP on both.
For some reason, my NAV twigs on it as hacktool, but her Corporate version doesn't. I've used TrojanHunter, HouseCall, AVG, Panda...all show nothing.
The following threads show others getting the same result, often with TweakXP lurking as the likely explanation. Hope this helps!