Mounting and read/write access to my Vista hard drive

Vista permits rather little in the way of file and directory access but using Knoppix 5.1 with
boot: knoppix 1
and mounting the Vista drive with
mount -t ntfs -o rw /dev/hda1 /mnt/hda1
allows almost everything. But for a small category of directories I am unable to
rm -vrf /mnt/hda1/dirname
even though I am root and there is nothing obviously protecting dirname in the way of privileges (that is to say, ls shows
drwxrwxrwx root root dirname
It is almost as though some level of Windows-imposed protection has survived, even though Knoppix is the O/S and root is the user.
Can anybody enlighten me (1) what it is that is preventing successful implementation of rm -vrf, and (2) what I can do to get round it, and so successfully remove dirname?
Thank you.