First of all you need Apache Server, PHP, MySQL and a Forum Script i.e. phpBB or Invision or vBulletin.
Download phpDev here
http://keihanna.dl.sourceforge.net/sourceforge/phpdev5/phpdev423.exe
and you get a bundle of all the things above.
Extract & install php dev. start the apache server, its 90% done.
upload the forum script to X:/phpdev/www/public
(x is your drive, usually C: )
now to access the forum through internet you will not know your IP address thru ipconfig command..
go to
http://www.whatismyip.com
See what’s your IP address.
now go to : http://your ip address/public/your forum directory/install.php
That’s it!