I don't have enough information to know just what your problem is, but I'll mention two things. The drive has to be mounted read/write, by default versions of Knoppix up to 5.x all defaulted to read only (I'm not sure about 6.x versions). You seem to already know about this from what you wrote, but I'm not completely sure that you mounted read/write so I'm mentioning it. Second, I very strongly suggest that the drive be partitioned FAT32 and not NTFS. Some people say that they can write to NTFS, but in the middle of a disaster recovery is not the time to experience another disaster.