It will work, but to share the internet connection like that the easiest way that I have found is to run a freeware proxy program, then set your browser/games/chat programs/whatever on the 5th PC to connect through the IP of the computer running the proxy, or in this case, the one with 2 network cards.
A free proxy program would be proxy+, available here
Let me know if you need any help!
A free proxy program would be proxy+, available here
Let me know if you need any help!