First, does your ISP allow for having a home server? Some do and some don't so it's best to check first. Second, are you inside of a LAN or is the PC directly connected to a modem? If you're inside of a LAN you'll also need to configure the routing device to allow it to broadcast information and allow outside incoming connections to be made.
I use Apache2Triad, a program that nicely combines Apache, PHP, mySQL, and modPerl into an easy to setup and configure system. Another easy to use application (that's also free!) is called EasyPHP. It provides a basic Apache server environment and supports PHP scripting. Both are available free for Windows OS machines.