I found this in the flightsimworld forum -
a guy in the french FSX forum at www.libertysim.net found a great tweak !
Most of the ones who tried this DOUBLE THEIR FPS ! (35-40 FPS !!)
The tweak is to replace the FSX.cfg by a good part of the FS9.cfg. Then at the next lauch, FSX will add a few lines to the new FSX.cfg. And then you can enjoy those 30+ FPS !!
http://www.libertysim.net/forum/viewtop ... 80&start=0
I did this to my XP Pro Sp2 with FSX Sp2 and it looks nice.