Intel core 2 duo 2.4 ghz
250gb hard drive
256mb nVidia GeForce 7900gs
Should run fairly decent. I'd say mid-range settings.
The Core Duo part of your CPU will have not performance effect. The cache that the CPU has although will. Your memory is a little low. I would double up your memory, I saw a great leap in start up by going from 1GB to 2GB. Your video card should be fine for mid level settings. This FSX is a monster. I would recommend a SLI or Crossfire motherboard solution which is what I am electing to get with dual video cards. One to rund the X and run to run the Y and this should help allot on FPS.
PS: Don't feel bad this sim is making my PC look old too!!!!