USU is an operating system for your computer. Unlike some other popular operating systems (like Windows, or Mac OS) it is completely free to download, use, modify and share. It is created with the idea to be useful in the educational sphere, and to be ready for everyday use. USU has three different editions: USU Mini is the core edition of USU, which includes the most important components. This edition is ideally balanced between offered capabilities and ease of use. It is suitable for home or business use. USU Desktop is the most completed edition. It contains substantially increased number of various applications. This edition has a strong focus on the possibility of being used in education. It includes a few dozens of high quality educational applications. USU Desktop can be easily integrated in any school, because of its completely free license. USU Netbook is specially created for the little mini portable computers, know as netbooks. It is based on optimized USU Mini along with additional software. This edition gives a full desktop feeling and works good even on the slowest netbooks. USU is based on one of the most popular Linux distributions Ubuntu. USU is created by Svetoslav Stefanov and Krasimir Stefanov. We will be glad to receive your questions, suggestions and comments and support. The project is widely open for everybody.