One of the biggest energy wasters in your yard is an unlikely culprit: the computer on your desk. That's because you probably never shut down the darn thing.

Of the 104 million PCs in the American workplace today, 60% are not turned off regularly and 20% never are, according to 1E, a London-based PC power management software firm. Users either don't want to wait to boot back up, or they think their IT departments want machines left on. Others erroneously think it's better for a machine to stay on, a misperception held over from the PC's early days.

Nationally, leaving on all those machines translates into $1.4 billion in wasted energy costs each year, 1E estimates. In your business, that's $25 to $75 per machine per year.

But more than just money, your computers also are helping kill the planet. Research firm Gartner estimates information technology now rivals global air travel in terms of greenhouse gas emissions into the atmosphere. Roughly 40% of those IT emissions come from computers that are left on.

So, what can you do? Simple. First, always turn off your machine at night. Second, adjust the power management functions in your control panel to turn off the monitor and hard drive after 15 minutes of inactivity and to go into standby mode after 30 minutes of non-use.

You need to remember to disable your screensaver, too. Contrary to popular belief, screensavers don't put your computer to sleep. They actually keep it awake, wasting energy. Since you've already set your monitor to turn off automatically, you won't have to worry about your screen getting burned., an IT support firm that caters to consumers and small businesses, will walk you through these steps over the phone for free through its "Green Your PC" program.

"Our goal is to change those settings on 100,000 PCs, which will have the same effect as planting a thousand trees," says Marc Itzkowitz, director of product management at Companies such as 1E and its competitor, Verdiem, offer power management software that automatically turns machines on and off. The cost is around $25 per machine, and payback is usually reached within the first year. "The opportunity for companies to save money, while having a positive impact on the environment, is enormous," says Matt Heinz, Verdiem's marketing director.

Finally, you should recycle or donate your machine when you're done with it. But beware: old PCs often get exported to the Third World, where child labor is used to extract base metals from them. "These shops are in the backyard, and they'll literally have kids bashing into monitors and breathing in very fine, toxic dust," says Barbara Kyle, national coordinator for the Electronics Take Back Coalition, which maintains a list of responsible, non-exporting recyclers on its Web site.

Instead, make a tax-deductible donation of your old machines to a local school or charity. Your local trash disposal agency, which is trying to keep computers out of landfills, should have a list of organizations that will take your machine.

–Joe Bousquin is a contributing editor for ProSales.