D3 DLL Missing

[Stratify]

When I try installing Action! on Windows Vista I get a prompt message saying this:
This application has failed to start because d3d11.dll was not found. Re-installing the application may fix this problem.
It is bugging me crazy. Please reply and fix this issue ASAP
And I tried downloading the DLL and put it in my Mirillis folder and my Windows folder!
Please fix this issue, I am about to shoot myself! PLEASE!

[radi]

This is a system dll file. Check if it's not infected or corrupted by third party applications.