OS Circular is a framework for Internet Disk Image Distribution of software for virtual machines, those which offer a ‘‘virtualized’’ common PC environment on any PC. OS images are obtained via the stackable virtual disk ‘‘Trusted HTTP-FUSE CLOOP’’. The system is designed to utilize Mirror servers and Proxies for highly-scalable worldwide deployment. OS Circular easily and efficiently handles both partial and periodic OS updates, including a rollback facility to ease experimentation with new OS images that might not be ready for production. This paper describes the design of OS Circular and the techniques to reduce the network traffic for quick downloading and booting.