Chrisitine, please make sure you setup your router with security, it's essential. Remember Stephen having someone freeloading his internet? This, or worse, could happen. Make sure your firewall in the router is switched on and enable WPA2 wireless encryption. Put a password on your router settings.
I rarely use the wireless feature on my router but found when I did switch it on and tried logging on via a laptop, I could log on to one of my neighbours network a lot easier than I could log on to my own! His router was "straight out of the box" settings. I could have encrypted his network and password protected his settings so that only I could use it, but not him.
As for anti-virus, I suggest Kaspersky, available at a very reasonable price here:
http://www.aria.co.uk/Products/Softw...roductId=28025
or NOD 32
http://www.aria.co.uk/Products/Softw...roductId=30947
though NOD32 is anti-malware only, it does not include a software firewall. If you get your router setup correctly the need for a software firewall is reduced. NOD32 has the lowest impact of any anti-virus/malware on overall performance. If you've been using Norton (uugh) you'll think you've got a whole new machine if you swap to NOD32, or Kaspersky for that matter.