TCP/IP Stack

Not an easily undertaken task. What operating system are you trying to do it on? For general information on what stack programming looks like, you could take a look at the Linux source code. It contains the source for its stack. There are many good reasons to reprogram the stack. Unfortunetly, it is tricky. There is a book by Jeremy Bentham, called TCP/IP Lean that claims to have the source for a simple stack with a web browser built in.

This is a link to a good description of the stack
http://www.it.lth.se/~matsbror/itd_exjobb/home_pages/tcpip_axis/report/node4.html

There are alot of resources out there.

I am gonna guess you need to know how to remove the TCP/IP stack in Windows 2000.
Open up Device Manager (right-click My Computer -> Manage -> Device Manager).
Click View -> Show Hidden Devices
A whole bunch of new stuff comes up under the heading Non-Plug&Play Devices.
One of these is the TCP/IP Protocol Driver. Right-click it and choose Uninstall.
Reboot when done.

Now to be honest, I do not know exactly how you would reinstall the TCP/IP stack. When you reboot, Windows 2000 might detect the TCP/IP is missing and it might automatically reinstall it.
Or you might need to add it using Add/Remove Hardware. This is my best guess.

But that should do it.