Add-ons not showing up in game. please read !!!!!

I am a newbie to FS2004, but not to computers, I have read all the read-me files and installed the add-on aircraft to the
C:\Program Files\Microsoft Games\Flight Simulator 9\Aircraft\XXaddon
as well as the gauges and effects, the aircraft.cfg files look correct, but in the game there are no additional aircraft.

This is a great game, esp the multiplayer. I work with T6A ands T38 A/C simulators (real ones) and I really want to fly those versions of the planes in the game.

Any Suggestions would be greatly appreciated!!!