Error was "The procedure entry point CreateDXGIFactory2 could not be located in the dynamic link library dxgi.dll". I've had similar errors with Unreal before (with DXGIGetDebugInterface1) which I think are to do with the fact I'm on Windows 7 (though they don't usually stop the game from running). Based on everyone else's positive feedback though, I seem to be the exception not the rule, so I wouldn't worry about it. =)