If you are booting the Knoppix 3.6 CD to a full graphical KDE desktop, then you should have hard drive icons on your desktop. Try using those icons to access the NTFS C: drive. If the icons on the desktop work for you & you are able to access the NTFS drive and do not want to learn more about this problem, then you can stop reading now.

Linux in general limits what the user can do. This prevents dangerous tasks from being performed without permission. You have just run into an example of where it prevents you from mounting the /dev/hda1. You will need to append the sudo command in front of your mount command. The other thing you may need to know if that NTFS is supported by read only & not read/write. Someone else may need to correct the command below, but it should allow you to mount the NTFS C: drive in read only mode.
Code:
sudo mount -t ntfs -o ro /dev/hda1 /mnt/hda1
I hope this helps.
James