how do you stop a program from calling home?

ok,
I got a program, it calls home to verfied the info that was inputted
if it's ok, it's reg, if it's not, it reverse back to eval or demo
I have been tolded in order to stop it from calling home you
set your firewall up and then it can't phone home .
ok, but noone is telling me how to do this. I'm running winnt 4.xx
on a public computer, so the basic questions are:

(1) what program is running to allow the software to call home?
(2) what software do i run in order to stop it from calling home?
the settings,the port,etc..
(3) will these settings work for every program that calls home?

please enlighten me if you can..


sooooo confuseddd