Microsoft has dominated the PC OS market with Windows, and latterly Vista, while Apple has remained in a distant second place. However, the arrival of low-cost subnotebooks such as the Eee PC range from ASUSTeK Computer has boosted the market presence of Linux. Microsoft will continue to control the notebook market, but the subnotebook segment is set to become increasingly competitive. This Perspective examines the likely challengers, and assesses their strengths and weaknesses.