No-one has mentioned the most important step to keep yourself safe.
Do not log on using an administrator account! Same goes for Linux or Mac logging on as root. Just don't do it.
Windows 7, keeping up to date with patches and not running as admin will protect you from most nasties without even lifting a finger. Add in call100s' recommendations, sprinkle a little common sense on top and you're safe.
Been doing this for years and don't have any of the problems this forum is so often adorned with - often I think because folks are just too lazy to log on using normal user accounts or are, sadly, ignorant of the risks.