Overwriting another flash

in Software
Hey guys,
does anybody know how the software will react if I try to flash a ECU that already has been flashed with another company software?
I have a customer with a woolich racing flash, but he is not happy about it, could I overwrite his flash like a normal stock ecu?
Or the ftecu software will refuse to write?
Thanks
Comments
Hi,
Our software should be able to overwrite theirs no problem.
Thanks,
Jason A.