If you are reading this late reply, it's worth noting that even the most powerful PC on the planet can be made to struggle with FSX. It all depends on your scenery complexity, autogen density, and the number of detailed AI planes that are within visual range. From experience, I would say that 38fps is quite a high framerate to maintain when you approach highly detailed scenery like UK2000 Manchester Xtreme. I don't check framerates when I use FSX, since I prefer to base my opinion on how smooth it runs, and whether the aircraft that I am flying is fully controllable. However, I would be very surprised if my framerates at Manchester could be maintained at 38fps, and I have an i5 2500k @ 4.3Ghz/8GB DDR3-1600 RAM/1GB GeForce GTX 560Ti powered system. That's because I run FSX at the highest detail settings, using highly detailed payware planes, with Ultimate Traffic 2 AI set to 100%, TreeScapes custom autogen, and AA/AF at 8xS and 16x respectively.
I get decent performance at UK2000 Manchester Xtreme using these settings, and there is no way that I would want to reduce any of my settings just to maintain a framerate of 38fps. I can fly quite happily with half that