Creating a firewall for winXP

heya,
I am going to be coding a firewall for windows xp (ie not a dedicated external firewall, an application single user),however, looking at various resources-i'm getting confused on where to start. Am I going to need to write a driver? Or is it possible to use something like windump?
Any advice on how to get started and where to look would be great.

Cheers,
n3wt

or perhaps rather i mean WinPcap insted of windump

apologies that ikeep replying to my own post!!!

Q-17: Can I use WinPcap to drop the incoming packets? Is it possible to use WinPcap to build a firewall?

A: No. WinPcap is implemented as a protocol, therefore it is able to capture the packets, but it can't be used to drop them. The filtering capabilities of WinPcap work only on the sniffed packets. In order to intercept the packets before the TCP/IP stack, you must create an intermediate driver.

So i guess that answers that question. Any resources /guide/help on how to go about creating an NDIS intermediate driver then?
cheers