Windows 7 comes installed with DirectX 11 which is compatible with DirectX 9 and 10. You do not need to install DirectX 9 or 10.
The game will require the .dll s to function, these are often installed with the game. This should be found in the install files or on the disk provided assuming it is a legal copy.
Not always the case i have an 1156 platform with a 5850 and DirectX 11.
The game Medieval 2 would not play until DirectX 9.0c was installed.
i downloaded this update and all was well.http://www.microsoft.com/downloads/en/details.aspx?FamilyID=2da43d38-db71-4c1b-bc6a-9b6652cd92a3&displaylang=en