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.

The answer to your question - no you have to re-install XP under Linux.