"This tutorial provides step-by-step instructions on how to
install XEN on an Ubuntu Hardy Heron (8.04) Server System (amd64)
without compromising on disk I/O and network throughput. You can
find all the software used here in the Ubuntu repositories, so no
external files or source compilation are required.
"Xen is an open-source para-virtualizing virtual machine monitor
(VMM), or 'hypervisor', for the x86 processor architecture. Xen can
securely execute multiple virtual machines on a single physical
system with close-to-native performance..."