—People increasingly put more than one OSes into their computers and devices like mobile phones. Multi-boot and virtualization are two common technologies for this purpose. In this paper we promote a new approach called OS switching. With OS switching, multiple OSes time-share the same computer cooperatively. A typical implementation can reuse an OS’s suspend/resume functionality with little modification. The OS switching approach promises fast native execution speed with shorter switching time than traditional multi-boot approach. We describe the design of OS switching as well as our implementation with Linux and WinCE, and evaluate its performance.