We think its because the 64bits D3DX dll which were put by accident in the setups.
We're trying to fix the setups ASAP.
Keep updated on the news, new setups should be ready later today.
Sorry for the inconvenience !
Moreover you must have Admin privileges and probably UAC disabled in Vista to be able to register correctly the DLLs

A working fix is to get the good 32bits D3DX9_35.dll and D3DCompiler_35.dll from DirectX August redist or from another site and put them in System directory. Try then to register the dll manually.