Win Xp Domain Logon erorr

I have a home computer running Xp professional which is connected to a home network, DSL modem, and router. For some reason I can no longer logon. I receive an error after entering the correct password or entering no password which reads, “The specified domain either does not exit or could not be contacted”.
The domain is not specified this would be the default. I have been entering the same password for the last year with no problems.
Just let me clarify the logon screen is the graphic with defaults the user id and you just enter the password. I even tried booting in safe mode using the admin ID, same error message.