How do I firewall a computer so that all network traffic pass through the VPN tunnel?

I would like to firewall a computer so that all network traffic (inbound and outbound) pass through the VPN tunnel. The VPN service is bought as a subscription from a commercial VPN service provider.

If the VPN connection is down all of a sudden, all network traffic will terminate immediately.

When the computer boots into Microsoft Windows 7, if the VPN connection is not established, there will be no network traffic. Network traffic is possible only after the computer connects to the commercial VPN service provider.

Any help would be most appreciated.