How to get PHP to recognize other extensions?

I'm fairly new to PHP and recently decided to install it on my computer with PWS 4.0 so I can do my development without having to be reliant on my host. But it only recognizes the PHP files with the *.php extension, not files with the *.php3 extension. I need this because right now, my web host only recognizes the *.php3 extension. Using PHP 4.0.1pl2 installed in PWS 4.0 on Win98SE. Thanx. <:3)~~ http://www.gerbilbox.com/newzilla/