WEB SERVER help

Hi all, I am a fresh graduate out off uni and i need some ones helps. U see our company has a HP server which came with win2000 server OS cd. I have installed win2k and have installed IIS on it. I am trying to have our web site (build on PHP and MYSQL). After a bit of trying, i got PHP to run with IIS, but then i realised that IIS takes a lot of time in process the PHP scripts. So i then stopped IIS and instaled Apache web server. Apache was faster in process the PHP scripts then IIS. Now my web server is working fine. But i can't get it to be accessable outside the server. I can only view my web site on the server and not on any of the other computers. I get an ISA Server Error, saying that gateway no access . Please help me, i am not that well vesed with server setup.. Please do email me on coolstudprit@hotmail.com Thanks prit