By default Knoppix allows you to use the hard drives for reading only. If you wish to write to a hard drive partition, you need to explicitly tell Knoppix to make the partition writable, this is to protect you from messing up your system by mistake.

To make a partition writable, right-click on the icon for the partition and select "change read/write mode" and it will ask you to confirm that you want to make the partition writeable. You can make the partition read-only again by following the same steps.

Note that you should not make an ntfs partiton writable unless you are using the captive=ntfs system as you may corrupt your files and cause serious damage. ntfs is the file system used by default for Windows NT/2000/XP though all can use fat instead. One way to check is you can right click on your drive in Windows and select properties to check what type of filesystem it is.