Multiple virtual hosts on IIS

For reasons beyond my control, a site I'm working on will be hosted on NT/IIS instead of Linux/Apache. One of the things I had been using was Apache's ability to specify per-site configuration settings to set the PHP include path for each virtual host. Is there some equivalent configuration option under IIS? It's trivial to make one site work using the global php.ini but I need to have several sites with different settings. I don't like the idea of putting php.ini files in every directory with scripts, and that doesn't seem to work in any case ("Access violation" or a cpu-chewing inetinfo.exe), although that may just be the regular php.ini crashes and not a multiple .ini problem.