I would strongly recommend VirtualBox as being the solution to your
problem. You can install Vitualbox on Windows and then install Ubuntu
Linux or the other way round - I run Ubuntu 8.04 with Virtualbox and
XP installed under Virtualbox, but on my wife's machine I have Vista
with Vitrtualbox and Ubuntu 8.10 installed under it.

Once the installation is over, everything runs very seamlessly. XP
runs as an application under Ubuntu and is just a click away. The best
thing (for Windowphobes like me) is that I don't have to load XP
unless I really need it.

I agree that VirtualBox is best as long as he gets the non-free one, PUEL,
rather than OSE. It has more options that he will want, such as usb
connectivity. VirtualBox also allows him to run in Seamless mode which is not
available in the free version of VMServer. This gives him a shared desktop with
his GNOME panel at the top and his Windows panel at the bottom an a shared
desktop.

I have stayed out of this conversation up till now, but am not sure that this is
even what he wants, although it is the best solution. He cannot use his current
Windows installation from VirtualBox or even in Linux. He must re-create it and
that means a separate licence from M$ to be legal and even then technically it
is not allowed by their licensing the last time I looked. Maybe they have
loosened up. I am not sure. Maybe somebody with more Windows knowledge can tell
us the legalities of the Windows EULA. It is physically possible to install from
his current Windows CDs, but it is not legal, as far as I know.