I don't see a How To, on this wiki, specifically designed to address the task of creating a Microsoft Windows XP virtual machine as a Xen guest under CentOS 5. Many of the concepts are covered in http://wiki.centos.org/HowTos/Xen/InstallingHVMDomU, but it appears to leave some things to the reader. I (EdHeron) would be willing to make the attempt at a page to focus on this task. It could be HowTos/Xen/DomU-WinXP-Install.