can't copy entire hd


anyone know how I can copy my entire hard drive over to a folder on a different drive? I keep trying it the old way, holding down Option and dragging the hard drive over, but it keeps giving me errors saying i don't have privileges to do it. I've tried a number of different things but nothing has worked. I tried logging in as root, I tried typing in 'su root' in the terminal and still nothing...

any help please???? thanks!