Listen, I've gotten a PIII 450, w/ GF 420 *MX* 64mb, 256 RAM to produce a 25 FPS in AH2 on the runway, offline. Granted when I hit the air it drops, to best 15, unplayable. ;-( But it's a PII450, I don't expect it too do better.
If this machine can get 25 on the runway, a ATI 9800 with a decent CPU will get MUCH more.
You have a bottle neck somewhere, it could be in the BIOS, Buss system, AGP, driver settings and on and on.
Admittingly I am a former old AW Video Tech game staff geek. So I'm just throwing in my old hand at this. I have seen these symtooms before.
I have made many a machines sheeit an get it in my earlier days before AW death. If I can do it with a PIII 450 GF420MX you can do MUCH better with a Ati 9800.
YOUR job is to find the bottle neck. When you do, all the other tweaking you did on the way will come to light and that machine will pound nails through brick walls . Trust me here, keep the faith.
Personally, I would start in the BIOS. Below is a link to my old site which contains MANY MANY tweaks, and a BIOS page that can REALLY help you a lot. IF you have Windows XP there should be a page on which services can be shut down.
Most of all it reminds me of a bottle neck or background processes.
Also make sure there is absolutely NOTHING running in the background. This includes OE auto email checking and MS Office FindFast. this must all be disabled. What I do is make a new user desktop that starts up VERY raw, only mere basics in the background.
AH Tech Hangarhttp://www.icongrp.com/~stagemon/ah/
This site is currently being EXTREMELY reconstructed, and about to replace the old site soon. The new sight is going to probably shock a few people in it's size and interface, I think the AH community will really like it, even compared to the old AHTH site which is still in operation. I'm not going to go into what the new site contains, but it's the most monsterous site I've built yet. I think former AW pilots will love it because of the interface, but who knows. ;-)
Anim