The best OS for GP3 ?

Having recently installed GP3 on my PIII 766, 384Mb, 65Mb Geforce 2 - I'm frustrated at the slow down that occurs when even a few cars are in front, when I start a wet race from mid grid this becomes truly desperate!

I have this system purely for running a couple of games and have a copy of Windows 98 to hand - will this run the game better than my current XP Pro?, will the 1.13 patch work in 98?
Also is there anywhere I can download GP3 2000? Is this a worthwhile upgrade or can i get the same results from downloading the numerous patches I see around?

I have a Geforce 6200 128Mb sat in the cupboard. Will this help me any 'cos I keep reading how GP3 is mostly about processor speeds and not too much about the video card.

Any help greatly received.

the best OS for gp3 is Win98b....

1000% sure