Here is the complete story regarding DirectX 9 on Windows 7 64-bit, including why you need it, why the default installation isn't enough, and the specific "better" method to ensure everything runs correctly.
Short checklist
Double-click DXSETUP.exe and accept the agreement. The installer will scan your Windows 7 64-bit system and add only the missing components. This will not overwrite your DirectX 11 files; it simply lives alongside them. Is 64-Bit Support Included? directx 9 download windows 7 64 bit better
For the most stable and comprehensive installation on Windows 7 64-bit, use the DirectX End-User Redistributable (June 2010) rather than the "Web Installer". Here is the complete story regarding DirectX 9