para – virtualize to install from iso copied for posterity

In order to boot from cd or dvd you need to change the guest virtualization type from HVM (fully virtualized) to PV (paravirtualized).

xe vm-param-set HVM-boot-policy="BIOS order" uuid=[uuid of your vm]

After you have booted from dvd, change back to fully virtualized mode:

xe vm-param-set HVM-boot-policy="" uuid=[uuid of your vm]