I had similar problems and did a web search for "XP" and "password" using a Linux distro (Ubuntu) off a computer magazine cover disk.
I found a cd image file for a bootable Linux program which showed all the passwords.
Ubuntu was able to create a cd using the image and I then re-booted using the cd.
Found it easiest to just reset the problem password to 'Blank' then change it once I got back into XP.
Sorry I can't remember the name of the program but I found it easily enough.
