You know it's so good to see someone who has evidently done a bit of homework, and understands the issues involved with p2p.
As far as I know avg is excellent, others on the forums use and recommend it. Scanning anything before you open it is a good habit to get into. You can expect AVG to catch a few viruses. It proves it is doing it's job
The third thing you should consider is Peerguardian. Put simply it blocks huge numbers of organizations from accessing your computer, who could otherwise enter and snoop around it to their heart's content. This is the website for Peerguardian
http://phoenixlabs.org/pg2/
Legality. Yes people in the UK have got into trouble for using p2p illegally, including parents whose children have been using p2p to share copyrighted files without their knowledge. Whenever you use it (or visit ANY website) your IP becomes visible to anyone you are connected to, and p2p users can be traced because of this.
If you exercise a modicum of common sense, you are unlikely to be "caught" using p2p illegally. I mean if you share the entire top 40 albums 24 hours a day, or several DVD rips of movies from the last month or two, then you are asking for trouble. And I know of Britons who have been prosecuted for selling CDs made off Limewire downloads. My sympathy is not with them
But really there are no sure fire guarantees, so please don't assume that there are so many users they will never be caught......
An assorted share of a few hundred files, and bear in mind many files are not copyrighted at-all or carry Creative Commons licenses, should not attract attention. I'm not exactly sure what the penalties are, but am aware that many cases do not reach court in the USA, rather being settled out of court. I feel the prosecuting parties may well be happy about this sort of outcome
I hope this helps but please ask if there's anything you want to know.
Oh yes. and..... in the event of action being taken, which might involve the seizing of hard drives, and also in the event of computer breakdowns, it is always a good idea to have a separate back up of all your valuable files
Take care
Hobo