function ScreenSaverEnabled: Boolean;
var
status: Bool;
begin
SystemParametersInfo(SPI_GETSCREENSAVEACTIVE, 0, @status, 0);
Result := status = True;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
if ScreenSaverEnabled then
Caption := ‘Screensaver is enabled.’
else
Caption := ‘Screensaver is disabled.’
end;