I've been messing around with FS2004 for about a week. It seemed no matter what slider settings I changed I was stuck with about 15fps in outside views and 11 or so in the cockpit of the Cessna 310.
My system is a toshiba 5200 laptop, 2.0GHz, 512 mb RAM, Nvidia GeForce 460 Go with 64 mb video ram (very cool machine, by the way :)).
For some strange reason it never occured to me that the card setting might be a problem. I fiddled with the anti-aliasing but never actually turned it all the way off. Last night I downloaded the 44.03 video drivers and while messing around I turned of AA and voila! Frame rates shot up.
I am now getting well over 20 in some views, although I plan to lock it at 20, and 15 most of the time in the cockpit, with outstanding performance in the virtual cockpit.
Before, clouds would bring me down to 3-4 fps, now I can use 3d clouds, medium or dense setting, and things are great. Full overcasts, etc.
In hindsight, I realize why the sliders were not affecting the sim: the anti-aliasing was overriding everything and keeping the frame rates low. I am obviously going to do more testing with various settings now because I can probably get close to 25 fps.
If you have a Nvidia mobile card this might be worth a try. Before, I thought that FS2004 might not be for me, now I'm happy!