I've technically sold my iMac (Mid 2011) to a relative as I have no need for it anymore and I have a newer macbook pro with Yosemite. I have a few specific questions. -Before I wipe it I am waiting for a 2nd hdd to be delivered so I can have 2 back ups of that computer. Is time machine okay for this? And how do i test the back ups as such? -The iMac currently runs Mountain Lion. I believe it shipped with Lion, do I leave it how it is or update it to the latest OS or what? Does making time machine back ups effect how they could be restored in later OS's? -Once I wipe what exactly is the procedure? Though this is only going to a relative I would still like to know my hdd has been wiped properly in case he is to ever sell it on himself. -How would I reinstall the OS once it is wiped? -and Finally any other things I should bare in mind before ridding myself of this machine? Thanks in advance. PS. Sorry if this is the wrong forum, this was the closest matching thing I could find.