I was able to sign in under administrator in safe mode, but not in normal mode. I don't know where this default name on the log on is coming from. It is the original owner, but she hasn't used the computer for a couple of years. I checked the user account in control panel, and only admin is listed. I also checked in the program accessed by "run", "control userpasswords2". The only user names in there is admin and guest. I am going to reinstall windows tomorrow. Hopefully this will clear up the situation.