Due to ongoing issues with compatibility in XEN, this package will no longer be included in RouterOS starting v4.4 (next release).
We have made a new virtualization system called KVM. This system should be compatible with your existing XEN images, and the settings in KVM are the same as you had them in XEN, with the difference that KVM has more settings and is more advanced.
Important! KVM only works on CPUs that support hardware virtualization. See the KVM manual for a complete list of supported CPUs: http://wiki.mikrotik.com/wiki/Kvm
MikroTik will fully assist anyone that needs configuration assistance to migrate from XEN to KVM.