FSX doesn't only allow users to fly fixed-wing aircraft; they can also download and install helicopter and rotorcraft expansions too. Most people buy Microsoft Flight Simulator X in order to pilot large, commercial aircraft and civil jets, however there is also a market and niche group for helicopter add-ons.
Image shows a Bell-Boeing V-22 Osprey tiltrotor aircraft in FSX. While not technically a "helicopter", this does fall under the rotorcraft section.
In this section, there are many well known and popular helicopters from manufacturers such as Bell, Eurocopter, Hughes and Boeing. Featured in this section are a range of civilian passenger helicopters, as well as military and combat choppers such as the well known Apache attack helicopter which has been used in many desert combat operations around the world.
There are also many helicopter missions available to compliment the add-on packages, which are viewable here.
Installing these downloads is just as easy as any of the other aircraft or packages on the website and most of the files come with detailed installation instructions and "readme" documents inside. If you are having a hard time, there are many tutorials on our forum which will explain in detail the procedure - users can also create a new topic specific to their own problem.
Helicopters are much harder to fly in any flight simulator package, and in real life for that matter - there is a lot more going on in the cockpit of a helicopter compared to that of a fixed wing aircraft. As well as controlling pitch, rotor angle and engine speed - pilots also have to control many of the other systems that go with it.
Many users complain that "helicopters are impossible to fly in FSX", but they really haven't given them a chance. Users must be patient, persistent and once they get used to the different method of flying, they are usually very happy and include rotorcraft flight into their daily "flight simmin'" routine.