So I have an iMac with Snow Leopard still (which I do not plan on changing) and my father who is sick just lent me his iMac. He is downloading Mountain Lion and said that it told him he would be asked for his Apple ID. I want to use the computer for messenger etc. but do not want to lose all of his iTunes settings and/or other settings. What I am wondering is which ID will I have to use to login to iCloud?? Mine or his? .....and installing Mountain Lion will not do a fresh install right? We do not want to lose his files.......Thanks!