Probally A newbie Question: Why does it try to download my php file?

I was using Linux for my intranet. It worked fine, but my cousin told me about how I could also use windows as a intranet server. I got rid of Linux (It was giving me a headache) When I installed Apache and php. When I go to access install.php (Or any php file), it downloads it off localhost (My computer) but never executes it, but it just returns me to a index screen of my files. I have checked the config files, they look ok. I have loaded the module into the httpd.conf and it looks like it's running, but it still doesn't work. Anyone have any ideas? Thanks BorgKiller