"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..."