Will DirectX 11 be available for Windows Vista or Windows XP?
DirectX 11 is built into Windows 7, and it is available as an update for Windows Vista (see
http://go.microsoft.com/fwlink/?LinkId=160189). This includes the Direct3D 11 API, DirectX Graphics Infrastructure (DXGI) 1.1, 10Level9 feature levels, Windows Advanced Rasterization Platform (WARP) 10 software rendering device, Direct2D, DirectWrite, and an update to the Direct3D 10.1 API to support 10Level9 and WARP 10.
For the same reasons noted in the preceding question (Will DirectX 10 be available for Windows XP?), Direct3D 11 and related APIs are not available on Windows XP.