1. Will upgrading to yosemite on macbook pro late 2011 cause my itunes library to erase? 2. Will upgrading to Yosemite repair a sound glitch issue that occurred after I installed Boom. (Boom has been properly uninstalled but the glitch is still there - tinny etc. 3. If I reinstall the operating system, will I lose itunes library? 4. Can one resinstall the operating system oneself without a disk? 5. I want to remove my HD and put in a 1 TB HD and put the contents of old onto the new. I know how to do this, but will I be able to put the operating system into it myself without a disk? Operating system is 10.8.5 mountain lion Thanks for answering.