What I do, to get the best of both worlds... [smiley=thumbsup.gif]...!
I have both FS 2004
AND FSX on my Hard Drive, and I just swap between the two Sims to use the compatible scenery, objects, etc, suitable for each Flight Sim...

...!
I am regularly selecting between the two Icons on my desktop...FSX/FS9!
...not to mention, FS 2002, CFS 2, Flight Unlimited II, Pro Pilot '99, Flight, etc, all on my HDD!...

...( I lead a very sheltered life!...

...!).
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.