Opening a Qemu/Xen file based VM Image (won't boot after upgrade)

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http://serverfault.com – Apart from one Virtual Host still running Xen/RHEL5, all our virtual capability is hosted on KVM hosts with LVM storage devices. I've stupidly attempted an Ubuntu full release upgrade on a guest running on the Xen machine, only to have it install a non-Xen kernel and refuse to boot (rookie error there). Getting to the actual issue, the machine in question uses a single file based storage device. It's been a while since I've had to open one of these, but the process shouldn't be much different from opening an LVM volume, but for some reason I'm not seeing a partition table in device file. r (HowTos)