You can do the cat /dev/hda thing with ntfs, but you can't untar because Knoppix can't write to windows 2000 drives.

For some reason, copying an EXT2 drive with knoppix takes much longer. For that I type mount and read the pid of the auto mounter and kill -9 it. Then umount everything that is /dev/hdsomething or /dev/sdasomething

Also this will make the drives with identcal partitions so if you are going from a 20gb to a 40gb you'll have to make another partition or resize it using fips or something like that.

If you want to make a compressed image of the drive you'd first want to dd if=/dev/zero of=/dev/hda the source drive before loading anything on it so that the unused space will compress very well. Then remote mount a file system (samba or nfs) and
cat /dev/hda | gzip -9 > /mnt/remotefs/blah.img.gz (something like that, the > may not be necessary)

If you already have a full drive that you want to duplicate do something like dd if=/dev/zero of=/junkfile.tmp that will fill the empty space with zeros and then delete the junkfile.tmp after it dies from a full filesystem.