[RESOLVED] How to add dwmapi.h in VS2005?

I want to draw modern shadow for a Dropdown Topmost window, but I don't know how to add this header file in VS2005 for my ATL project. Where is this Header file and how to add it?

fatal error C1083: Cannot open include file: 'dwmapi.h': No such file or directory

I am sorry I ask such basic question. I never used c++ for 20 years.