New PC ???

[jwenting]

Pretty much anything you buy these days in the midrange or higher will run FSX quite nicely.

On my decidedly meager specs (by current standards) I get quite acceptable performance.
It's a Core2 Duo E4300, 4GB RAM, 2x250GB SATA2 harddisks, ATI 3870 videocard (512MB vidRAM), and a separate soundcard (seems to make a bit of difference to some machines for performance, and just sounds a lot better).
Add an Asus P5L1394 motherboard (do get a decent motherboard, as the cheap ones have slower bus speeds, pulling the actual performance of everything else down, probably a major factor in the performance problems many people have who buy cheap off the shelf PCs) and I get 20-30fps just about everywhere even when flying around in aircraft like the LDS767 over 30m terrain with real weather, and that with everything set to medium/high.
Only things I keep turned off are aircraft shadows, lens flare, and I turn down the 3D clouds to something like 70 miles.
I do that for performance reasons and (in case of lens flare) because it looks ugly.