Lenovo has announced the Blue Sky desktop computer, claiming it to be its smallest, quietest and most energy-efficient desktop.

The new ThinkCentre A61e (its formal name) ships next month. About the size of a telephone book, it weighs 8 lbs, and is about 25 percent smaller than the previous ThinkCentre model, Lenovo officials said.

Blue Sky is also the first full-functioning PC to run on 45 watts of power, meaning it can be powered by a solar panel or roughly the amount of electricity needed for three compact fluorescent light bulbs, a Lenovo spokeswoman said.

It will run either the AMD Athlon 64x2 dual-core processor or the AMD Sempron processor, with several choices of ultra-small hard drives, ranging from 80GB to 750GB. It has 4GB of memory and comes preloaded with either the Windows Vista Business or Windows XP Professional operating system.

The Blue Sky measures 8.5 by 11 inches in size - the same as a sheet of paper - and it's 3 inches thick, about the size of large phone book.

Lenovo expects the Blue Sky to do best in the small business, education, medical and financial sectors, where desktop space is limited. It features a low-speed fan for quiet operation.

Blue Sky derived its code name, which has stuck, for its environmental sensibilities. It is made up of 90 percent reusable or recyclable materials, and its packaging is 90 percent recyclable. Because of its energy efficiency and recyclable materials, it is Lenovo's first product to win a Gold EPEAT rating from the Green Electronics Council.

Lenovo said the ultra-small PC could be a success, noting that research firm IDC has forecast more than 52 percent growth for that product segment from 2005 to 2010.