It is not recomended that you go through with the hd install of knoppix, try downloading kanotix, it is a distro largely based from knoppix with more debian packages to make it more suitable for life on the hd. First thing I would need to know though, are both drives "normal" internal hard drives or are one of them a usb drive, and which drive would you like to install onto and which hard drive has your windows partition and how many gigs of space is used?