I went on to my macbook air, and I saw that there was a computer in my 'shared' thing. I didn't know what that was, so i thought maybe it'd go away if I restarted the computer. So I turn it off, then try to turn it back on. It makes the tone, the logo shows up, the little spiny thing appears, it spins for about 30 seconds, then it makes a click noise, then the screen goes black and it's shut down again. The internet had been slow all day, and I really need to know what happened. I have plenty of important stuff, and I can't really afford a new computer.