I'm having an odd issue with a windows xp computer belong to an older family friend. A few days ago, out of the blue, she found herself unable to login to any of the accounts on the computer. Windows would consistently say "invalid username or password" even though the password had not been changed.
I used http://pogostick.net/~pnh/ntpasswd/ to blank out the passwords for the accounts. Rebooted and then reset the passwords back to what they used to be. Things seemed to be working fine. However, 4 days later, she called to say it wasn't working again. Any idea of what the root cause could be and how to prevent it from happening again?