TomTom One, unit and the maps

TomTom one- you cannot use this map on this device.

I'm getting this message on my old "ONE" because I corrupt the map files some how....

SO... I have a exact TOmTom one... ( I have two units. the same model number)

SO I just erased the memory on the old-bad unit and copied the contents of the memory from the Good unit to the Old unit...

It start up, but I think I saw it said miss matched device serial number to the map..

so How do I fool it into thinking it has the right serial numbered map?

Thanks for your help...