Did my little trojan worm infected computer put the kibash on this new ssoftware I'm trying out?
No, its not the trojans. Its Norton.
NAV doesn't play well with other av programs, and its not a good idea to have more than one
resident av installed anyway as this can cause conflicts (yes, even if one is not running). I'm a little surprised you were even able to install avast! without first uninstalling Norton.
my current crappy antivirus
Most of the forum members are converts form other av products, so I won't argue with your description at all. To really give avast! a try you will need to uninstall nav first, then try a repair of the avast! installation. Make sure you are online, go to open add/remove programs in the control panel, click on avast! and choose the repair option. I think you will be happy with the results of your efforts.
If your have trouble uninstalling nav there are removal tools available. It can be difficult to get rid of.
As far as the password, most av programs have password protected virus signatures. This is a good thing since it prevents other av programs from scanning the signature file and reporting lots of infections. Panda AV is the only exception to this I know, but there may be others.
If you really feel you have trojans you should also download and scan with Ewido. Its very good at finding and removing trojans and should not conflict with other av products.
Hope this helps, and welcome to the forum.