Yesterday, in a long-expected but controversial move, officials of the One Laptop per Child (OLPC) project announced that their green-and-white machines, designed for children in developing countries, would run Microsoft Windows as well as the project's novel Linux-based interface. In an interview two weeks ago, the project's founder, Nicholas Negroponte, said that the move was necessary to enable the mass global acceptance of the machine, something he had long predicted.

OLPC's laptop will be available in a "dual-boot" configuration, with customers able to choose either operating system. "The people who make decisions on what to buy are not the kids," Negroponte said. "They are ministers and executives. They are very comfortable with a laptop that they know. The fact that the machine can do both is a huge advantage. Plus, you have a huge developer community that does software that works on Windows."

The decision adds cost to the laptop. To carry a second operating system, the machine will require more memory, which will cost an extra $7, even if Windows is never booted up. And any government that does choose to boot up Windows will pay Microsoft an additional $3 per machine in licensing fees. For those using Windows, the final cost will be $198, up from today's $188. (The costs will be higher for five unnamed countries in which Windows-ready machines will receive a trial run. For those machines, an extra memory drive was added at a cost of about $20.)

The move to adopt Windows is the latest twist in the sometimes turbulent story of the project. OLPC is a nonprofit organization founded in 2005 by Negroponte and others from MIT's Media Lab, with the goal of building a laptop computer that was rugged, usable, and inexpensive enough to reach millions of poor children in the developing world. As recently as 2006, Negroponte was predicting sales of more than 100 million machines by this year. But OLPC's flagship XO machine has not caught fire in the global marketplace. So far, about 500,000 machines have been delivered, mostly to Uruguay and Peru.

Until now, the XO has employed a custom user interface called Sugar, built on the open-source Linux operating system. OLPC's ex-president Walter Bender--who resigned last month in protest over the impending Microsoft deal and was replaced by Charles Kane, OLPC's finance chief--announced yesterday that he was launching a foundation, the Sugar Labs Foundation, to advance Sugar, which he helped to develop.