Just did a test install of Ubuntu within Windows. It's a very easy
installation and one that an "average" computer user could cope with.
The downside, of course, is that Ubuntu is at the mercy of the Windows
files system. That shouldn't be too much of a problem.
Buoyed by that success, I tried it to do it with Windows 7 Beta. No
such luck! Microsoft has changed the boot system and as a result
Ubuntu won't boot to finish the installation. It's possible there are
a few hacks to get around that. I haven't done any research. No
doubt Canonical will devise a way of making it work with Windows 7. I
suspect an attempt to do a "manual" install of Ubuntu would result in
Windows 7 no longer booting.
Michael