xbox won't recognise originals

[Hull_chipper]

I've just got a machine in for repair but the owner apparantly doesn't know what he has done

It boots up fine until you put an original game in the tray. The error message familiar to trying to trying to play a back-up in an unchipped machine appears on screen.

Any ideas what this guy has done & whether the machine can be fixed?

I've not opened up the machine yet, as I won't take liability for it without further info from him (which he can't provide) so I don't know if a diy chipping job has been attempted.

Thanks in advance