Did you try the following?
- failure to install the latest DirectX 9c version. Even though windows 7 comes with Direct X11, you might still need to install the newest DirectX 9c version to run A6. For A7 and A8 I know that this is neccessary for sure. See if there is a "d3dx9_30.dll" file in your game directory. Try deleting it if it is there or moving it there if it isn't.