It's a big deal when a major corporation pledges to cut its carbon footprint--every detail of energy and transportation use needs to be taken into account--and it's an even bigger deal when a company as large as Microsoft says that is will reduce its carbon footprint by 30% compared to 2007 levels in the next three years. The company hasn't provided details on its 2007 carbon emissions, but it's safe to assume that Microsoft will be making some serious changes.
Microsoft has already outlined a broad plan to improve energy use in buildings, cut air travel, and increase the use of renewable energy. The company is already working  on a $1 billion corporate campus expansion that will include under-floor cooling systems as well as lights that sense movement and turn on and off automatically.
And the company can always use its own software to assist its effort--Microsoft's recently released Environmental Sustainability Dashboard  helps businesses measure and cut energy consumption and greenhouse gas emissions.