Sven
As explained by Jendrik, the "AppleTV" format will work on non-hacked
Apple TVs. If you are creating a quicktime compatible container,
whether they work on a non-hacked Apple TV will depend on the codec
originally used. Generally speaking if you have an "avi" file that you
then put in a quicktime container with iFlicks, it's unlikely to work
on a non-hacked Apple TV.
I don't know how much you know about the hacking, but it is very
straightforward these days and does not involve opening the little box
of wonders. Simply install from a usb stick. A factory restore will
remove the hack if required later.
Simon