>> how exactly would you be sure the user saw this message and is what replies yes to it?
>> do you even know what video cards are installed in the system? let alone what mode they are in or which of the displays are hooked up to a monitor?
> Because it would be displayed by the firmware at boot time
but it's not boot time that you are installing the OS.
so do you give the warning the next boot after the change?
or are you trying to say that an OS install/upgrade should only be possible through the BIOS?