not sure what the problem is, but if you've installed the cgi (installer) version of PHP, you will have to modify httpd.conf -- add;
ScriptAlias /php/ "c:/php/"
AddType application/x-httpd-php .php
Action application/x-httpd-php "/php/php.exe"
and you may also want to add index.php onto the end of:
DirectoryIndex index.html index.html.var index.php
if you've not done that. then restart apache after that.
hth