You'll have to mount your hard drive first.
There may be a more elegant way to do this within Knoppix, but you can try this:
Create a directory named hdd off the / directory of your Knoppix 'disk'. Then, from a terminal window, try 'mount /dev/hda1 /hdd'. Then, do a 'ls /hdd' and see if you can see the content of your hard drive. If not, try 'mount /dev/sda1 /hdd' and again list the /hdd dir to see if your hard drive is mounted.
This is pretty much a long shot, but it might point you in the right direction. If you get errors when trying to mount your hdd, try adding the ntfs switch to the mount command as in 'mount /dev/sda1 /hdd -tntfs'
If that's not working, google around for mounting drives in Knoppix and see what you can figure out.
Hope that helps