First as mhtml stated, you will need a static IP and a server. I have some more detail for you.
IIS, Apache, PWS, 4d webstar, aol server, bad blue, acanor, covalent, domino, emwac, go ahead, hawkeye, I planet, java server or something else?
Install the software and then configure it according to your network settings. Open up port 80 on the firewall and if the firewall is ahead of the machine then it (the firewall) will need to be setup to pass thru requests.
Questions from me
Are you on 2000 or XP pro - ifs so, use IIS as this comes with both and if this is the case, then are you serving more than one site? If you are then you will be limited to 10 connections (simultaneous sessions) per site.
Some recommended sites - www.dslwebserver.com