to stop IIS manually:
you get a search result for the manager (Internet Information Services (IIS) manager, on the right side of it there are restart/stop/start buttons.
If you don't want IIS to start on startup because its really annoying..:
oh and IIS and xampp basically do the same thing just in a bit different way. ANd if you have Xampp for your projects then its not really all that nessecary to leave it on if you don't ever use it anyways.