I don't know if it's xen under the hood or not (not much experience with this sort of thing). However, 'xen' is mentioned in the following link which I'm following so perhaps it is xen related: http://docs.amazonwebservices.com/AWSEC2/2009-03-01/DeveloperGuide/index.html?ami-via-loopback.html I'm not all the way through this link so I can't vouch for it's utility but it's good thus far. Jason