Today at work I did a really stupid thing and deleted my usr folder from my Hard Drive. I don't know what happened but it just suddenly appeared and I knew it was an odd file that shouldn't be there so I thought it was junk and I trashed it. Now I can't reboot...I just get the spinning circle at the grey apple start up screen. I tried to reboot from the install disc by holding down the 'C' key but now I get a kernal panic and loads of words on the screen...how can I even begin to re-install my system when it doesn't get past the kernal panic??