A couple weeks ago Citrix bragged that its Xen open source virtualization widgetry would be pre-installed by big unnamed servers vendors by the end of the year.

Well, rival VMware Tuesday stole a march on both Citrix and the tangle-footed Microsoft and its promised Hyper-V technology and waved around signed contracts with Dell, HP, IBM and Fujitsu Siemens, definitely making it look like it’s holding four aces – at least for the moment.

The four OEMs, all already VMware partners and bound to support Microsoft as soon as Hyper-V, a reportedly strong contender, arrives in June, will all package up servers embedded with VMware’s free operating system-independent ESX 3i hypervisor, which runs on bare metal and is just plug-and-play.

Fujitsu Siemens has already started shipping; the others will in the next 30-60 days.

VMware CEO Diane Greene called it a “big step for the ubiquity of virtualization.”

ESX 3i, reportedly used by 100,000 customers, is a 32MB teaser to coax users over to the full-blown VMware Infrastructure 3 as well as an education in the concept of virtualization. Fujitsu Siemens will ship an evaluation copy of the Infrastructure suite.

Only 10% of corporate servers are said to be virtualized.