Jack O’Brien sent in this article from Ars Technica:
One of the most significant new features added in alpha 5 is support for Wubi, a new installation mechanism that makes it easier for Ubuntu and Windows to coexist on the same computer. Wubi provides a complete Ubuntu installer that can be run in Windows from the Ubuntu Live CD. It installs Ubuntu into a folder on the Windows file system and sets up a boot menu so that users can choose between Windows and Ubuntu when the computer starts.
Unlike a regular dual-boot configuration, Wubi doesn’t require users to create a partition on their hard drives for Ubuntu. When Ubuntu is installed with Wubi, it can be uninstalled directly from the Add/Remove Programs utility in Windows.