This game is very demanding on hardware. There are a number of options that can be adjusted to improve performance. From the main menu, select the options screen, at the bottom click the button with II on it to go to the 2nd page of options. Try reducing the percent trees down to 50 or lower. In addition the options in the Terrain section will also affect performance, try reducing the draw distances as well.
It is also quite sensitive to system memory, you really need to have at least 4 GB of system memory for this program to run.
If you are running the game on a system with shared video memory, this will also have significant effects on game performance. To check this: Start Run dxdiag.exe this will start a built in program to check hardware. Run it and look under the Display tab to see what you have.
Design Lead: Scourge of War
"My God, if we've not got a cool brain and a big one too, to manage this affair, the nation is ruined forever." Unknown private, 14th Vermont Infantry, 2 July 1863