Default we can create a Linux Virtual Machine on Xen server in CentOS, Windows HVM (Hardware Virtual Machine) also support on it.
If you have already installed Xen server with LVM can create and run Windows virtual machine.

Need to install necessary packages  on server, previous Xen Project-modified version of QEMU  we should have installed and not be needed in recent releases. Copy the Windows ISO file copy to specific directory.

For example I have created under /root/iso/. Hypervisor to start the domain in Hardware virtual Machine mode and boot from the DVD to install Windows.
Create Logical Volume (LVM) :

Set size to 50 GB. We have already created volume group name "vgroup0". Logical volume name "linuxfaq"

#  lvcreate --n  linuxfaq -L  50G  vgroup0
Logical volume "linuxfaq" created

# lvdisplay /dev/vgroup0/linuxfaq

 --- Logical volume ---
  LV Path                /dev/vgroup0/linuxfaq
  LV Name                linuxfaq
  VG Name                vgroup0
  LV UUID                CcSp3R-5k5f-DDrS-X32S-GrFv-avB5-xC9oa7
  LV Write Access        read/write
  LV Creation host,      time localhost.localdomain, 2015-01-20 20:56:22 +0530
  LV Status              available
  open                   0
  LV Size                50.00 GiB
  Current LE             20480
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto - currently set to     256
  Block device           253:64

Create a Configure file:

Now, create a configure (cfg) file, and add below lines with the name of windows.cfg  under /xen directory

kernel = "/usr/lib/xen/boot/hvmloader"
memory = 4000
name = 'linuxfaq'
vif = [ 'ip=,mac=00:11:32:13:42:5A,bridge=xenbr0' ]
address = ''
netmask = ''
disk = ['phy:/dev/vgroup0/linuxfaq,hda,w','file:/root/iso/Windows_Server_2012_R2_64Bit_2.ISO,hdc:cdrom,r' ]
vnc = 1
vcpus = 4
vnclisten = ""
vncunused = 1
vncpasswd = "thelinufaq"

Start Windows VM :
 #  xm create /xen/windows.cfg

Using config file "/xen/windows.cfg".
Started domain windows(id=40)

Find VNC Port number :

Find the virtual machine running port number for view remote system by VNC
# ps aux | grep vnc | grep windows

root     20552 37.1  0.0 256356  4048 ?        SLl  20:24   0:23 /usr/lib/xen/bin/qemu-dm -d 40 -domain-name windows-videoram 4 -vnc,password -vncunused -vcpus 8 -vcpu_avail 0xff -boot dc -serial pty -acpi -usbdevice tablet -net nic,vlan=1,macaddr=00:16:3E:1E:47:5E,model=rtl8139 -net tap,vlan=1,ifname=vif40.0-emu,bridge=xenbr0,script=no,downscript=no -M xenfv

# netstat -anp | grep 20552

tcp        0      0      *                   LISTEN      20552/qemu-dm
unix  3      [ ]         STREAM     CONNECTED     582054 20552/qemu-dm
 unix  3      [ ]         STREAM     CONNECTED     536241 20552/qemu-dm

Now, the windows VM running port number is 5116. Then, Install windows server on remote system same as booting from DVD.