I had the same problem and this is what I did to fix it... right or wrong, it worked.
Check your httpd.conf file to see if apache is seeing these lines:
#location of your .exe, note: "/"
Action application/x-httpd-php /php/php.exe
#Add your extensions
AddType application/x-httpd-php .php .php3 .php4
AddType application/x-httpd-php-source .phps
#depending on what you plan to use:
DirectoryIndex index.html index.htm index.php index.cgi index.php3 index.php4