Not very well at all to be honest. FSX takes a super computer to run at full settings, and nobody has the facility to buy such excluding Microsoft
But anyway yeah, I'de say with that rig on medium/low graphic settings and others on FSX you would get about 6FPS on the ground, 15FPS in the air. Lemme put it this way, the last computer I had which I no longer have for some technical reasons (Got refunded and decided to purchase one from Alienware) had these specs:
MSI P6n Nvidia 680i Chipset
Intel Core 2 Duo E6700 2.6 GHz
3GB RAM
500GB HD
2x Nvidia 8800GTX 765MB
620watt PSU
Windows Vista Ultimate
And guess what I got with that, an earth shattering 10FPS on the ground and 30FPS in the air with medium settings... Not a lot is it? To get FSX to run decent your going to need something like this:
Nvidia 680i Chipset
Intel Core 2 Extreme QX6700 2.6GHz (Quad Core - 4 CPU's)
2GB of RAM
Nvidia 8800GTX 765MB
1000watt Next gen PSU
Windows XP
Thats the new computer I recently ordered from alienware which came in at about £2,500 = $5,000
It's rediculous I know, the quad core processors are supposed to make a fairly big impact in FSX and I know that from a friend. Plus when SP1 comes out, the performance will be bumped up a little. Sorry to be the bearer of bad news, but your computer wouldn't run it well. Forget using Vista right now too, big mistake, wait about 6 months or a year then it will be worth buying.