"Wubi is an Ubuntu installer for Windows that lets you install
and uninstall Ubuntu from a Windows desktop. Wubi adds an entry to
the Windows boot menu which allows you to run Linux. Ubuntu is
installed within a file in the Windows file system (a loopmounted
partition), this file is seen by Ubuntu as a real hard disk. That
way the hard drive does not have to be repartitioned before the
Ubuntu installation. The resulting Ubuntu installation is a 'real'
Linux system, not just a virtual machine. Wubi makes it easy for
Linux newbies to play around with Ubuntu..."