I use Fedora 13 on my laptop, that means I have the full control on my root and user accounts. After I started the computer this morning, I found it fails to login using both user and root account: it prompts I entered wrong password. I rescued it using installation disk using following operations: 1: make a copy of /etc/shadow, 2: reset my password as it should to be. After that, I made a diff between backup /etc/shadow and the new /etc/shadow, and found it really changed! That means the password was really changed by something! Could anyone give me some clue about what happened? Thanks a lot!