A utility that parses all SimObjects in Flight Simulator to verify that model files are FSX native.
Simply launch MDLXChecker.exe and it will display a list of models that don't have MDLX in the RIFF header. If you want to check a specific simulator, you can use the following command line syntax:
MDLXChecker.exe -sim:value
Where value is one of FSX, ESP, P3D, or P3D2. If you launch MDLX Checker without any arguments it will default to any installed simulator.