I have OS X installed at home and I am therefore able to re-download it from the app store and to copy the installer on an USB drive.
My parents have a very bad internet connection and I would like to use my installer to install Lion at their home.
Is it possible and if yes how could I buy Lion with their Apple ID but install it from my installer?
Last question, I have an iMac 27 and my parents an iMac 21 both from the same generation, is the installer specific for a given machine or not?
EDIT: I do not want to reinstall my parents iMac, just to upgrade it to Mountain Lion...