Okay, I had/have an old imac, one of the big boxy all in ones. Before I really knew anything about what to do and what not to do with computers, I deleted something that obviously was needed in order for the mac to run. Now, when I turn it on, the screen is blue. No codes, letters...nothing. I still have pictures/videos on there I would like to get off, but am unsure how to get to them without having to take it to a store. I tried to safe boot it (f8) but am not sure if that is how you do that with a mac.