You can look here for info on Windows Defender: http://windows.microsoft.com/en-us/w...ndows-Defender
Are you using Internet Explorer as well? If so you can turn down the default security for the Internet (that is one of the specific zones) Security Zone: http://windows.microsoft.com/en-us/W...urity-settings
Windows 7 is a worthy upgrade if you don't mind spending the money. Then again, if you haven't had the laptop too long, the manufacturer might have a "Free Upgrade" seeing as so many people hated and refused to use Vista.
Win 7 is a great step up that addresses what most of us considered to be the major faults with Vista. Would be worth taking a look at. Also don't go without an AV program if you're surfing. AVG is on option so is Avast (my preferred free AV solution). I'm sure someone will chime in as well with something along the lines of a recommendation to dump Internet Explorer. If you chose to go that route (you cannot, repeat CAN NOT uninstall it) look at both Firefox and Chrome.