We do not work for Microsoft and we also can not get involved in legal matters.
There would be no need for them to burn it to an ISO file, asthat makes no sense..
You burn an ISO file to a CD/DVD.
The CD which came with the sealed package you sold him is a bootable CD containing the XP files.
He changes the Boot Order in the BIOS to make the CD Drive first in the Boot Order and installs from there.
But no one knows WHAT they are trying to install XP on.
Their device manufacturer would have to support XP being installed on that exact model number and supply XP drivers for it.
Saying it does not work is useless to trying to help them.