go over to cnet.com there is a ton of great free soft ware to protect your computer.
I run avira for my anti-virius, spyware terminator to protect aginst malware, and comodo firewall. cnet editors ranked them as their top favs along with a few others. I've been using them for a while and they have protected my computer very well.
edit:don't use microsoft IE, if you have to use IE7 at least. I'd recommend google chrome, works great.