We currently have XenServer 4.1 and XenServer 5.5 running. These are the free versions.
I am using XenCenter 5.5 to manage them.
According to articles like this: http://support.citrix.com/article/CTX123999
You are supposed to easily renew the license files.... but that option is not available for me. Any other way to renew the license files or in 21 days am I just screwed when it expires