Citrix XenServer Express Edition is a free, production-ready virtualization platform that enables everyone to quickly get started with Xen virtualization. Easily installed and seamlessly upgradeable, Express Edition is your on-ramp to Xen and the Citrix XenServer product family.
Citrix XenServer Express Edition offers all of the base performance, tools, and easy to use features of the XenServer product line and is built to run on the broadest range of standard server hardware. It supports dual socket servers with up to 4GB of RAM and can host up to four virtual machines on each system.
Citrix XenServer Express Edition can be quickly upgraded to the richer capabilities of Standard Edition or Enterprise Edition by the simple addition of a license key, with no need to reinstall software or convert guests.