There is no fool proof way execpt to pull the plug. But you can minimize the exposure.
Make sure your router's firewall is on.
Turn off respond to ping.
Make sure you are using WPA with string key, GRC.com has a generator to create one for you.
DO NOT RUN P2P SOFTWARE. or IE (too many holes)
Run Shieldsup from gre.com to make sure you have no ports open and runing in stealth mode.
Run AV, Firewall's, Spyware/adware scanning software. As for Spy/Adware you will need at least 2, none catches everthing. Have one running at all times and do manual scans on regular basis.
When PC is not needed TURN THEM OFF.
Good luck with your belkin, they come with added features like lockup's dropped connections. They are cheap and that what you get.