midnight_blue
Like you, I also worry about my computer being compromised because I use my PC for other things as well, i.e. banking, shopping, research, etc.
Now, I will be the first to admit that there is no such thing as 100% security and that using P2P brings internet dangers that much closer to you. However, there are some extra security utilities you could use to bolster your security.
PeerGuardian 2 (beta 5b)
http://www.methlabs.org
Uses IP block lists to keep out organisations that creep into your PC via port 6346 when using LW.
Prevx Home V2.0
http://www.prevx.com/prevxhome.asp
Sits behing your firewall and protects your PC against the worms, trojans, malicious spyware, malware and hacker attacks.
There are other security utilities that will help but I would suggest that you use these two and see how you get on.
UK Bob