An FSX Sea King would be awesome on the new helos front, preferably a Fleet Air Arm one. Really stupid question - do FS2004 aircraft work on FSX?
Some do, some do not. Usually, they will, but you have to ad a "thumbnail.jpg" to each texture file folder for it to show up on the selection panel. another problem that occasionally crops up is gauges not working, and some times the panel or the sound file will kill that aircraft from showing too, so you have to "alias" (there's some posts about that around here, and in the "Help" sections) or play "swap around" with panels and sound from aircraft that do work.
It's trial and error, some times.