well obviously you might have php but do you have a webserver??
if you do then webserver doesnt know how to handle .php files I guess.
you can try to rename it to .php5
idk hard to tell exactly with such short lame description
you know what best option I can recommend you is download and install AppServ and put register page in it(folder www).
move the content of default www to some subfolder inside www
hint and if you already have MySQL then I guess you dont need the one in AppServ to be running
hint you can uninstall/remove php or webserver if you gonna install AppServ
appServ have webserver php and MySQL all configured alltogether.
without reboot after install I think you will need to start a servers first.
address should be like

or change it for some other IP