Frustrating....At the initial install the game worked and I actually played through the tutorial. Then I decided to tweak the game to see if I could make the chit graphics more crisp. I set the resolution in the game to 1600x1200, exited the game and tried restarting. From then on, the game would not start. After 5-6 reinstalls (along with the supporting Microsoft apps) it still will not start.
Hm, please check and see if you still have a Western Civilization Software\Conflict of Heroes folder in your My Documents folder. If so, please delete it and try one more uninstall and then reinstall.
I deleted the directory and tried another uninstall and reinstall with same results. I even tried updating to XNA and .NET 4.0 with no impact on the problem.
One thing I notice on each reinstall (probably up to 10+ by now), even though my directx, .net, and xna are current, the game seems to not detect it and keeps reinstalling everytime. During that process it asks me if I want to repair or remove .net and xna and I assume I select repair.
Please try changing your desktop resolution and see if that helps anything. The error being thrown is likely being caused because your video card is reporting that it cannot create the necessary size and depth of graphics buffer.
edit: If you're using any display management type programs (such as Seamless Windows), please try turning these off as well. If you have two video cards (such as one on your motherboard without DirectX9.0c capabilities), try making sure that the video card without these capabilities is disabled. You might also try updating any video card drivers.