PHP - IIS7 Issues

I have installed IIS7 and PHP on my new Vista Laptop and had PHP working just fine. I started my computer up today and PHP is not working? The only thing I can think of that changed is that I develop multiple websites and change the Physical Path to the default website when I switch sites. I did switch site this morning but I do not know if it was working before that. I switch back to the site that was working yesterday and that site is not working anymore either. It isn't giving me any error like it did before I got it working. It is just stoping when it gets to any PHP code in my page. I look at the page source and the HTML is being served right up to the first bit of PHP code, not error that I see. Any ideas? Thanks, Bob