QUOTE(Heimdall @ Apr 14 2012, 03:33 PM)

What made you think that was an Xecuter 2 chip........?
Well - I believe its using an Xecuter 2 chip as it used to display "Xecuter 2" in small writing at the bottom of the boot screen. However - I know nothing about modchips (apart from how to flash them incorrectly!!)
I've decided that I have little or no chance of fixed this.
I've managed to get my xbox to boot by disabling the modchip and rebuilding the hard drive using xboxhdmaker (luckily I had an eeprom backup). I've then performed a soft mod, so I am at least back running unsigned code. I do now have to worry about locking the hard drive, but its a significant step forward from Christmas lights!!
Thanks for all comments - its been much appreciated.