function InstallScreenSaverA(hWindow: HWND; hInstance: HINST;
  pszFile: PAnsiChar; nCmdShow: UINT): BOOL; stdcall;
  external 'desk.cpl' name 'InstallScreenSaverA';
function InstallScreenSaverW(hWindow: HWND; hInstance: HINST;
  pszFile: PWideChar; nCmdShow: UINT): BOOL; stdcall;
  external 'desk.cpl' name 'InstallScreenSaverW';
{$IFNDEF UNICODE}
function InstallScreenSaver(hWindow: HWND; hInstance: HINST;
  pszFile: PAnsiChar; nCmdShow: UINT): BOOL; stdcall;
  external 'desk.cpl' name 'InstallScreenSaverA';
{$ELSE}
function InstallScreenSaver(hWindow: HWND; hInstance: HINST;
  pszFile: PWideChar; nCmdShow: UINT): BOOL; stdcall;
  external 'desk.cpl' name 'InstallScreenSaverW';
{$ENDIF UNICODE}

function InstallScreenSaverEx(const AFileName: string): Boolean;
begin
  Result := InstallScreenSaver(Application.Handle, MainInstance,
    PChar(AFileName), SW_SHOWNORMAL);
end;