Test PHP properly:
Download 'OSCommerce' from here: [
www.oscommerce.com]
Install it on your server and test if the PHP is working.
If it is working:
There is no problem with WampServer but a problem with your coding
If it is not working:
Either reinstall WampServer
OR
Fix the PHP problem in the HTTP Conf file
You could also use the Show PHP feature to diognose PHP for advanced users or see the version, might be a case of upgrading from PHP4 to PHP5.
Hope that helps,
:-)