If all goes according to Nicholas Negroponte's plan, there will be 10 million PCs in the hands of the planet's poorest children by the end of 2007. The $100 laptop, which technologist Negroponte and his MIT team have been working on for the better part of a decade, goes on sale in the spring. (Initially, the price will be $150.) Out of necessity, its various versions boast the most sophisticated low-energy computer tech ever seen - like a hand-crank power source and a chipset that consumes 13 percent of the normal wattage - and mesh networking so kids can share files without a server. Argentina, Brazil, Nigeria, and Thailand are lining up to buy them.