"Recently, however, Ubuntu added a second option for
test-driving a distro -- this time without even logging out of an
existing Windows account. This software, named "Wubi," will
actually run Ubuntu Linux in its own virtual environment within
Windows, without jeopardizing an existing PC configuration or
system data.
"Because Wubi loads and runs from its own dedicated folder on a
Windows hard drive, it actually runs faster than a live version of
Ubuntu. In fact, while Wubi isn't quite as fast as running a
fully-installed version of Linux from its own disk partition, it's
close enough that many people can't really tell the difference in
performance. That makes it a great tool for introducing employees
-- and managers -- to a "real" Ubuntu Linux environment while still
allowing them to work productively."