>I'm going to try to act on the NAV...it could have a little sense...though is not enough to sleep quite dreams :-)

Hope you will have, of course <s>

Actually, in my experience uninstalling Norton AntiVirus in particular can cause even more trouble than installing it. Windows newsgroups are full of reports.
FWIW, F-Prot works well for me since a long while. Kaspersky looks promising and gets good recommendations in the press (but I did not try it intensively myself yet)
There are free-for-personal-use AV tools available as well
http://www.antivir.de/en/products/antivir_workstation/?id=48&L=2&L=2
(Italian: http://www.antivir.de/it/prodotti/antivir_workstation/?id=48&L=3&L=3 )
http://free.grisoft.com/freeweb.php/doc/2/


Just my 2 cents
-Stefan