Fable on Sli mode in Vista-HELP!!!!

I juz purchased the M1730. Get the latest update for both graphic card and windows update for compatibility plus sli hot fix and sli is enabled and OS is Vista Home premium

I played other games such as Cold Fear and Jade Empire with max configuration, FE at 4x anti-aliasing and max details and they ran smoothly even the CPU only runs at 70% . Mine CPU is core 2 duo 2.2GHz!!!!!

However, when i played fable, hav 2 even turn off anti-aliasing, minimum details, mesh, shadows and effect with 800*600*16bit and the game stil runs like hell and lag alot . Couldnt fig out y????

I fig my Nvidia control panel as folow:
-Sli enabled
-anisotropic filtering: 4x
-antialiasing-gamma corrrection: on
-antialiasing-mode: Enhance application setting
-antialiasing-setting: 4x
-antialiasing-transparency: multisampling
-conformanct texture damp: Use hardware
-Error-report: off
-extension limit: off
-Force mipmaps: Bilinear
-SLI performance mode: force alternate frame rendering(I also tried the other two, Couldnt work!)
-Texture filtering-anisotropic sample optimization: On
-Texture filtering-negative LOD bias: Clam
-Texture fitering- Trilinear optimization: Off
-Threaded optimization: Auto
-Triple buffering: On
-Vertical sync: Use the 3D application setting

Any suggestion, dying for this game.....And thx