Assassin's Creed 2 PC is DX9 only
 

PC Games Hardware interviewed David Champagne, 3D Lead Programmer of Assassin’s Creed 2, about the highly anticipated PC version of the story around Ezio Auditore da Firenze. From the interview we learned that Assassin’s Creed 2 won’t support DirectX 10 or DirectX 11. But the PC version offers higher resolutions and better anti-aliasing modes than the console variants.



http://www.pcgameshardware.com/aid,7...DX9-only/News/

Doesn't come as a surprise, since consoles are not running DX10/DX11. XBOX runs on modified DX9