I have taken over my son's old Mac Pro (he has a new one). I have my own apple ID. The computer for updates etc still auto connects like it is linked to him. What can I do to 're-set' the name and auto link.

I have taken over my son's Mac Pro (he has a new one).

I have my own APPLE ID but with updates etc. the computer still acts like it is linked to his computer name and Apple ID account. Can I 're-set' it to rename and autolink it to my Apple ID?

Also the iphoto has and erro (QUIT) message and I have rebooted and even tried to restart with option and command quits depressed and tried a reboot but still get the same error??