Old game vs. monster rig

Hi all, first post

I got this nice setup that people from Homeworld 2 forums assure me will run the (demanding) 2003 game very well, yet it runs slowly, and it's clearly graphics. There's slowdowns when a nebula shows up in the background, for example.

The game was released when XP and Direct x9 where already out.

I have...
Wolfdale 3.16Ghz
ASUS Rampage Formula
EVGA GeForce GTX280
G.skill 2 x 2GB DDR2 PC2-8500
BenQ 24" LCD 1920 x 1200
Vista Ultimate 64bit

I might download new Geforce drivers, and even update to Windows 7, but I suspect this will only bring me further away from compatibility.

Should I (and how?) create a partition and install in it XP, Dirext x9, and x9-compatible graphics-drivers...since this game was at the time XP-compatible?

How'd you go about it?

I have the right patch (the only game patch ever released for the game), and am running in XP compatibility.

No difference whatsoever.

So you haven't downloaded the latest drivers for your GTX280?

Nope. Shall I now?

Yes, please do, it should be 191.?? or similar.

191.07, yes.

Still massive jerkiness. As crappy as when I was running this game in 2003 on obsolete hardware.
Sight. I waited years for budget to be nice to me, and now I have a superb machine and the same problems.

So I went ahead and freed up some space on my disk, and turned that into a new volume, about 10GB.
Used a bootable XP disk, installed on the small volume, and during the process it said the computer would restart and then Setup would continue.

Setup doesn't.

I'm again prompted to boot from disc at startup, but pressing any key doesn't work. Waiting doesn't work either. Gotta reboot, and then pressing the key is accepted...but guess what? The XP installation starts from scratch, replacing the other XP installation. Circular.

And what side-effect does this also have? It removes the Vista loader from the HDD, so now I cannot install XP, nor can I boot back into Vista.

Help?

EDIT: I'll be reinstalling the Vista bootloader from the VIista DVD, and if it works I'm back where I started, with XP refusing to setup completly in its partition.

If i'm reading this right, XP isn't installing properly? Thats a bigger problem I think.
But the OS really shouldn't matter for a DX9 game.

Some one help me on this one :|.

I finally got my Vista bootloader back on the HDD and Vista loaded successfuly.

So now I'm stuck where I started: old game compatible with x9 and XP, running on Vista 64 bit and x10, and running so slowly and jerkily that it cannot be played. All patches and drivers applied, XP compatibility mode on. Other users of this game are able to run it on Vista.