UNABLE TO OPEN NIS

Hi there

When trying to open NIS a message comes up saying "Unable to open this Nortan Product.  Please restart your computer"

I have tried restarting my computer and have done any updates.  I am able to open and use Nortan Utilities.  I do not have the product key anymore as silly me through it out so I cannot remove and reinstall or I will lose it all together.  Any ideas are very much appreciated.