Lagging in demo...

I have run Empire Total War on ultra settings with a very good framerate. When i tried running napoleon's demo the game lagged horribly.
My computer

Processor Intel i7-870 @2.93 Ghz

Graphics card Radeon Hd 5700 series

RAM 8 GB

Hard trive 1.5 TB hard drive

Mainboard : Dell 0G3HR7

all drivers are up to date.

The demo is not the released game and so far four updates. This is the reason I hate demos, personally.

The big question would be have you verified the demo's game cache integrity to see if it's missing something?

Gonna do that now

EDIT: Turned off the ATI HD Sound device and verified game files, now getting a solid 50-60 FPS in it. Can now consider buying the full game

Buy game its great.