Well, as documented through this thread, GP3 doesn't work all that well on windows xp (as you'd very well know).
I found that out the hard way, whacked in another hdd in my pc, installed win98 on it, installed GP3 and all the associated programs/tracks etc. and have never looked back. And yeah, I've got the latest win98 catalyst drivers on that hdd and haven't had any problems.
In response to your question, FSAA (Full screen anti-aliasing) is another term for AA and AF(?)
I'm not too sure if its possible to partition your hdd and install win98 on the new partition (XP might have an issue with that), but in my case, I have 2 hdd's, one is 80 Gb the other is 60Gb. I basically boot them up through my CMOS screen by selecting the IDE channel that I want to boot up (IDE 0 for win xp, IDE 1 for win98). But then again, I have a lot of old games that work infinitely better in win98 than XP, so that's why I've setup my pc that way.
You can set up your pc that way too, headache, but I'm a bit unconventional in the way I solve problems (but at least i have no problems afterwards!)