Well, after previously testing Windows XP in Xen and finding it was slow, I've now found when reading Red Hat Virtualisation documentation that para-virtualisation drivers exist for Windows.  Great :-)

So, now I must test again and see how Windows XP performs when these are installed.  Of course, installation might still take a while like it did previously, but the performance could be much better once you've gotten past the install part.  I mean, install is only install and only done once, whereas using the machine is every day (if you're in Windows a lot for one reason or another).

I will report later on my findings and how it performed.  Now, I'm using LVM as well, rather than simple image files which are inherently slow anyway.

Here's the link to the Xen website with all the info you need on the Windows para-virtualisation drivers:

Xen Windows GPL PV