[PvK]

A hardware NAT firewall, no software firewall, being careful and not running any kind of MS Outlook. Software firewalls are often worse than most viruses. Though if you're not careful or don't know how to be, then a non-obnoxious software firewall and/or anti-virus program might be good. However I would just run virus scans manually every so often, rather than installing something to constantly check, since that tends to interfere with and and slow down your computer. I like Ad Aware and Housecall, the free web virus scanner from Trend Micro.

PvK