After a years-long dispute, Microsoft and the computing and education project One Laptop Per Child said Thursday that they had reached an agreement to offer Windows on the organization’s computers. Microsoft long resisted joining the ambitious project because its laptops used the Linux operating system, a freely distributed alternative to Windows. The group’s small, sturdy laptops, designed for use by children in developing nations, have been hailed for their innovative design. But they are sold mainly to governments and education ministries, and initial sales were slow, partly because countries were reluctant to buy machines that did not run Windows, the dominant operating system. Education ministries want low-cost computers to help further education, but many see familiarity with Windows-based computing as a marketable skill that can improve job prospects.