All on the same server?? :eek
Hosting all depends on what you want to pay now doesn't it. And what is available where you live?
PHP can be run on NT alongside ASP, but I've not actually come across any ISP who offers that option. Quite the reverse indeed - it's one or t'other with most hosts. Try Rackspace or some of the other big players. If you can afford it you can have whatever you want.