Install Xen Vps System To Test Out

I'd like to install xen vps system to test out instead of paying Virtuozzo $1k+ for licensing.

I found this article:
[url]

I installed this on Centos 5 server. I got one tiny problem now:

[root@server ~]# virt-manager
Traceback (most recent call last):
File "/usr/share/virt-manager/virt-manager.py", line 304, in ?
main()
File "/usr/share/virt-manager/virt-manager.py", line 224, in main
import gtk
File "/usr/lib/python2.4/site-packages/gtk-2.0/gtk/__init__.py", line 76, in ?
_init()
File "/usr/lib/python2.4/site-packages/gtk-2.0/gtk/__init__.py", line 64, in _init
_gtk.init_check()
RuntimeError: could not open display

Also, that tutorial doesn't explain how to create actual vps

Anyone care to explain? Isn't there some web gui available for xen too?