BOOL SetLayeredWindowAttributes( HWND hwnd, // handle to the layered window COLORREF crKey, // specifies the color key BYTE bAlpha, // value for the blend function DWORD dwFlags // action ); Windows NT/2000/XP: Included in Windows 2000 and later. Windows 95/98/Me: Unsupported. Header: Declared in Winuser.h; include Windows.h. Library: Use User32.lib.