Vista - Command and Conquer 3 Directx problems

This is my first time on these forums so be nice please! =D
I've tried searching for this problem but they all tend to be the computers don't meet the minimum specs to play the game, which is not the case with me.
My specs are:
Quad Duo 3.2GHz i7
12GB 1600MHz Corsair RAM
Asus Rampage Extreme II MotherBoard
1.5TB HDD (500GB Raptor and 1TB external)
2 x 1GB nVidia 9800GT (Though my DXDiag shows them both being at 3GB each?)
Antec 1200 Gaming case with Water Cooling
And I'm running windows Vista Home Premium 64bit.

I have DirectX10 the latest version installed, but when I try to play C&C3 it comes up with this error:
"Please make sure you have DirectX 9.0 or higher installed. Also verify that your video card meets the minimum requirements, and that you do not have hardware acceleration disabled in the Display control panel."

So yeah, I have no idea whats up with it. But it ran fine on my old computer:
Duo 2.2 GHz
2GB RAM
integrated 512MB nVidia 8800 Graphics Card
Vista 32bit

Any help would be greatly appreciated =D

Download and install dx9.0c.
DX10 and 9 are different.

as roy said, even though directx 10 is installed, older games dont use directx 10, so either install directx off the disc or download directx9.0c from microsoft's download site...
to answer your other question though, your graphics cards are showing with 3GB because it uses system memory for caching.