Vista has Direct X 10 amd 9.0x installed, but 9.0x doesn't contain everything that 9.0c needs. You can however remedy this by intalling 9.0c and it will install what's missing. I'd already donne this for other games before I reinstalled DiF, so it may be a factor. Having DirectX10 and 9.0C installed at the same time does not seem to cause any probelms, programs seem to know which they need.