If you build it, it can be green. That is, if you're savvy in the components you choose and in how you use your PC, you can cut your electric bill and get a good, warm eco-friendly glow. But will you get all the computing power you desire? Such are the potential trade-offs.
Read all about green gaming PCs, extreme green machines, and more at Ars Technica: "Ars System Guide special: it's easy being green"