Used to have NAV on my old Dell laptop (installed by manufacturer), but once allowed a virus thru` which then managed to stop NAV from removing it. Had to go thru` long process of manually removing the virus, using advice from another source.
Now have Avast anti-virus on my desktop, which regularly picks up on & deals with potentially infected e-mails as they reach mailbox (NAV never did this). Also Avast has a free version (altho` this one requires you to manually run virus scans - not a problem in my view) and updates itself automatically (& very much more regularly than NAV). The On-Access scanner and the virus scans are easily adjustable, whereas I seem to remember NAV wasn`t. Whenever I`ve had any queries, Avast have answered them within a day by e-mail, whilst NAV either directed you thru` a usually useless FAQ section on their website or gave you a premium rate helpline phone number.
No contest!