You can run about 65,000 different webservers (if that many existed), since the most important thing is that they run on different ports. If you run Apache on 8000 or 8080 or something like that and IIS on 80 then you’re all set. Or don’t run both simultaneously, that works too.
I tried IIS 6.0 and it’s still not as granuar as Apache, with you being able to set everything in the config file. It seems too imprecise for my taste. Of course, now you too can run .NET ASP on Apache so … ;-)