Computers, if left on all day unattended, waste energy.

In fact, according to these helpful tips (PDF) from the National Institutes of Health Environmental Management System, you should turn off your computer and monitor if you plan to leave them idle for more than two hours.

There is, however, another option. Meet Folding@home, a “distributed computing project” of Stanford University in which people worldwide run software during their computers’ off hours to do protein-folding research and scientific calculations.

More than 1 million computers or CPUs since 2000 have helped create the equivalent of a one of the largest supercomputers in the world to help fight protein-related diseases including Alzheimer’s, Parkinson’s and cancers.

And it’s not just limited to home desktops. My husband, Matt, recently used his brand spanking new PlayStation3 — automatically loaded with Folding@home on versions 1.6 or later — to join the largest surge in Folding@home activity ever thanks to the PS3’s release in 2006. Matt’s PS3 displays the actual folding process in real-time at the molecular level as well as a map of Earth with points of light for all the other participating users worldwide.

If your XBOX is failing — and many of them are — this is yet another reason to bite the bullet and check out the slightly pricier PS3, especially if your XBOX is on repair for the second time, which is the case for Matt.

“It’s a way for console owners to feel like they’re making the world a better place — and not just by killing aliens and evil ninjas — and for wannabe PS3 owners to convince their socially conscious wives that the XBOX versus PS3 surcharge is a little bit for a good cause,” Matt said.