I have a windows 7 box that I was trying to pen test... I began with the basic chntpw on ubuntu.. trying to clear/change the password. When I rebooted into windows the passwords I had "set" was not valid, the password was not cleared (for another acct) and the Administrator account had not been enabled as I had selected. I continued to try using chntpw but eventually gave up.
Now on BT4 I've tried bkhive, and john but neither seems to be working (both are throwing me errors)
BKHive:

root@bt:/mnt/WIN/Windows/System32/config# bkhive system /root/key
bkhive 1.1.1 by Objectif Securite
http://www.objectif-securite.ch
original author: ncuomo@studenti.unina.it

Error opening hive file system


and
John:

root@bt:/pentest/passwords/jtr# ./john -format:NT /root/ipass
Loaded 1 password hash (NT MD4 [128/128 SSE2 + 32/32])
Crash recovery file is locked: ./john.rec



Does anyone have any ideas as to why this is happening and/or what I should do about it.

PS although I don't want a direct answer (A start in the right direction would be nice), I'm at the point where I really do just want to make sure I haven't screwed things up too badly so solutions and help are much appreciated