Ubuntu/Backtrack eth0/wlan0 Missing

My good deed for the week was to offer my laptop as a replacement for one with a screwed VGA port.

'Yeah just switch the disks' - Linux is clever, it will work it out. #FAIL

Dual boot with Ubuntu 11.10 & BackTrack (Ubuntu).  Both failed to connect to the network and had created eth1 & wlan1 interfaces.

Google took me to http://www.orzeszek.org/blog/2010/07/25/fix-missing-eth0-when-cloning-ubuntu-vmware-virtual-machines/

Its discussing the same problem, but in a virtual environment.  The conclusion is the same in that the MAC address has changed and Ubuntu stores this as a reference in :

/etc/udev/rules.d/70-persistent-net.rules

Delete the file, reboot, problem fixed.