I was troubleshooting an issue my brother was having with his Macbook over downloading files, installed Firefox for him, ran Apple updates... and while the updates were installing the computer froze. He restarted it, and on startup he got a circle with a slash through it. I've been googling and checking forums and I tried booting into safe mode (Shift at startup, I believe?), and putting in the OS X disc that came with it and booting from that (C at startup?) but I get nothing. It just goes from the Apple with the loading circle, to the picture of the slash circle. I'm not too Mac savvy but help would be appreciated to walk me through it a bit. Perhaps I'm doing something wrong. I'm not really sure on the specs of the computer or the OS version, as I'm rarely on it.