Hi Tiger
your system will run CFS3, but it depends on how much eye candy you want to see.
It has taken me two computer upgrades to get to the stage where I can max out all the slider settings in the game and still get good frame rates.

So load up the game and start to play around with the settings. One tip I would give ,is that you change your settings from the cfs3 config program and make sure you go through the "exit" option to save the changes. (I believe there is a bug so you must save this way for the changes to take effect).
Also try and run the game resolution the same as your desktop.

Over at Sim Outhouse there is a great thread about how to set your pc/cfs3 up and tweak things.

If you are going to spend any money on your system to get more eye candy/frame rates then  I would get a better graphics card and more ram.

I hope you enjoy the game. There are lots of add ons now, and I would strongly suggest you get the free upgrade/patches from MS to make the game run better.

cheers
chuck