Guardian: You will have spotted the ballyhoo by now – Microsoft’s new Windows 7 operating system is out today. And, rather as when Microsoft launched Vista three years ago, the company is trumpeting its energy-saving credentials. Windows 7 offers “more than just lip service” on eco-friendly features. Microsoft is not making any specific claims about how much power Windows 7 can save, though in a demo for journalists in California recently, a laptop playing a DVD achieved 20% more battery life …