Does aligning a deskjet printer's heads stay in the machine or stay as a parameter in the computer's drivers ?
In other words, can I align the printheads with a PC and use the "tweaked" printer with a other one ?

Yes, the printhead alignment data is stored in the printer an is therefore considered portable.

Thanks. I thought so. I changed the cardridges of a Dell 720 printer and the unofficial Win98 drivers do not allow prinheads alignement. So I aligned them with an XP portable. Now the cardridges are unofficial aswell.