This paper introduces VaporDisk, a fast, reliable and portable Windows mixed kernel and user-space file system. This system is designed for use by the "casual computer user", i.e. someone with little or no technical knowledge and is therefore is designed to be  entirely transparent to the end user. It is also designed to work with the simplest back end storage systems, such as Amazon's S3 while being extensible to later take advantage of more complex data models.  VaporDisk simultaneously provides almost the same performance as a local disk, minimally impacting the user experience. This is accomplished with a write-through cache and smart revision collapsing, described in detail in the paper. Additionally, VaporDisk provides a friendly and secure web interface to allow remote access of files from an HTTP server, making data portable to any device with a web browser.