As you have got this up and running, I would have tried to mounbt the Windoes disk partition manually if I were you.
Assuming you have got Knoppix 6.X with the LXDE interface up and running, you have a screen icon as #3 from left on the bottom status line. Click that, and issue fdisk -l on the command line to find out what disk partitions Linux can see.
Often the main partition will be listed as /dev/sda1 (first partition on first drive), and you can try to mount it read-only with the mount command, using the sudo prefix to take on super user privileges for the occasion, check available space with df, go to the root directory of the volume with cd, then use the directory command ls to see files:
Code:
sudo mount -o ro /dev/sda1 /media/sda1
df
cd /media/sda1
ls -al
If this doesn't work, the drive problems may be more serious, and Knoppix might not be the right tool.
If you can get so far, you can use the cd command to move to the directories of interest. Having found the files, you can connect USB media (sticks or hard disks) for backup, mount them and copy over to them with the cp -a command. (Don't bother if the -a option gives you some warnings.) Assuming the USB storage is recognised as /dev/sdb1
Code:
sudo mount /dev/sdb1 /media/sdb1
sudo cp -a * /media/sdb1
Afterwards, you can unmount the partitions (sudo umount /media/sda1; sudo umount /media/sdb1) and halt the system.

Good luck!