I had no luck getting php to compile on IIS 4.0 when it was included in a asp page. Perhaps 5.0 will process the php code, but I didn't bother trying. You can get it to work if it is within a frame however. But frames basically suck, so I gave up on that on the site I was working on, lol
This issue is totally www server dependent, I've heard it works on apache on a win box. Have not tried it myself though...