Hey Guys!
I would highly suggest using a paid software or a combination of a free versions of both a firewall and antivirus, such as AVG free and Comodo Firewall or maybe Zonealarm (doesn't work that well with Vista, so Vista users beware!!)
Hopefully we will have new antivirus solutions for vista, all i know is i use Norton because of the speed and reliability (since its older versions at least, NIS 2003 wasn't the fastest...

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-Gerardo