Well I am not 100% sure, But I accidently changed my permissions on my HD on the desktop to no access, and drop box. It froze my whole computer up, and when I went to restart it. It gets past the apple screen but then it gets to the blueish screen and then a loading circle appears and just keeps circling and never makes it past that. I thought it had to do with the permissions I set to no access and drop box. After all that I went to use terminal, by booting up using the original mac install disc (I have tryed repairing permissions using disk utility, but as soon as I click repair permissions it says there is some kind of error doing it says something like "the underlying task reported failuire on exit") so i jumped to terminal seeing if I could fix it with a sudo command I found on the internet, but when I type sudo in, it just says command not found. I need some help can anyone?