PHP 5 and IIS 6 Problem

Hello everyone, I'm quite new to PHP so please excuse with my lack of knowledge. I am running PHP 5.2.6 on Windows 2003 Server with IIS 6.0 ISAPI. After installing, I am having two, probably related, problems. 1. It appears that PHP is working, however, it only works for some of the domains. For instance, I have mydomain.com and PHP is working but it doesn't work on the identically configured test.mydomain.com with identical pages. The test.mydomain.com throws a generic 404 error. 2. Some PHP sites that I host (I don't develop in PHP) will have pages that will not render at all. For instance, I have a photo gallery that the index.php renders correctly but when you navigate to any other page, you get a completely black page back, including the source being blank. I might just be overlooking something obvious but I've been wrestling with this for a few days now and can't seem to figure it out. Any help is greatly appreciated! Ryan