What do you mean by "I've installed the Windows 7 iso edition..."? Just burn the .iso file to a DVD and install. When you bought the download this should have been explained to you. Call the retailer, or Mircrosoft, if you're still having problems - when you buy software you should expect a basic level of support.
Don't worry about what partition to make active - the install process will take care of that. If you don't really know what you're doing it's best not to mess about with things like that.