[piasabird]

I have seen some motherboards for desktops that use a Pent-M Processor. Aopen sells some and also a couple bare bones kits. With an integrated video solution it barely uses 37 watts with one DVD and one hard drive. The drawback is that the motherboards are expensive and the processors can be pricey. However, Toms hardware had a review on this and when they installed the cooler sometimes the fan did not even run when it was idle.

This is kind of radical.

This is an approach which seems to make sense even thought it would mean a more expensive computer. In the long run you would save money on the electic bill to make up the difference.