IIS/PWS Config done by PHP

Hi, I'm curious to know how PHP configures IIS/PWS to let itself handle all requests for files ending in .php, etc. How is it done? Is it the same for IIS and PWS? Is the configuration different for using PHP as a CGI and as an ISAPI module? PHP puts a string value under the "Script Map" registry key, but adding just a new string value for a new file extension doesn't work. So this can't be it? Thanks heaps. I've wanted to know this for more than a year now. Posted a lot of messages to useless Microsoft IIS newsgroups but never got any response! James