need help with 2 networks on one machine

This is the problem I'm having , running windows xp pro, have 2 nic cards one on board and one pci. One is configured to access an office network that requires its own software and security protocols to run. The other is connected directly to a broadband cable modem.

The problem I'm having is that for some reason internet explorer wants to use the office network card to access the internet and although it is possible the speeds are very very slow. If I disable the office network card the computer is forced to use the broadband connection and everything works fine.

What I want to do is somehow direct all http traffic through the broadband card. Any suggestions?