Included here is an example of how to run a Windows vm (DomU) in Xen. Purely for reference.

#
# Windows 2003 STD - System Centre Configuration Manager
#

import os, re
arch = os.uname()[4]
if re.search('64', arch):
    arch_libdir = 'lib64'
else:
    arch_libdir = 'lib'

kernel = "/usr/lib/xen-3.2-1/boot/hvmloader"

builder='hvm'

memory = 1024
shadow_memory = 8
name = "sccm"
vif = [ 'type=ioemu, bridge=eth0, model=rtl8139' ]
# dhcp = 'dhcp'
disk =  [
        'phy:/dev/datastore/sccm-system,hda,w'
        ,'phy:/dev/datastore/sccm-data,hdb,w'
        #, 'file:/media/iso/sccm_2007_sp2.iso,hdc:cdrom,r'
        ]

device_model = '/usr/' + arch_libdir + '/xen-3.2-1/bin/qemu-dm'
acpi=1
apic=1
localtime=1

# boot on floppy (a), hard disk (c) or CD-ROM (d)
# default: hard disk, cd-rom, floppy
boot="dc"

sdl=0
vnc=1
vncconsole=0
vncpasswd=''
vncunused=1
vncdisplay=3
stdvga=0
serial='pty'
usbdevice='tablet'