As part of an effort to play up the environmentally beneficial aspects of its products, Microsoft is offering small businesses a chance to win 5000 gallons of regular unleaded gas in its Small Business Gas Sweepstakes. The contest runs until July 18 and is open to U.S.-based small businesses with between 2 and 100 employees.

On the contest homepage, Microsoft lists 5 tips for small businesses looking not only to cut energy costs, but also to help the environment. For example, Microsoft says Windows Vista can save organizations as much as $70.77 in energy costs per PC, per year compared to a typical non-Vista PC. "It saves you money and lets you give Earth a little hug," according to Microsoft.

Companies can also use Small Business Server (Microsoft doesn't specify which version) to set up and run an integrated virtual office that allows employees to work from home and save $100 a week on gas, according to Microsoft.

Microsoft also notes that Office Live Meeting allows companies to hold online, face-to-face meetings for as little as $23/month.

Despite the contest's playful tone, reducing power consumption is a serious goal for Microsoft, which has previously pointed out that Vista uses just 3 watts per hour during idle time compared to 100 watts per hour for XP.

Microsoft has also slashed power consumption in Windows Server 2008 by 40 percent, which is part its mission of making its growing collection of data centers as energy efficient as possible.