cannot log you in as domain not available

I have an IBM T43 with XP Pro SP3. There are only two user accounts on the machine, a guest account and an admin. When booted up today the machine gave the error “The system cannot log you on now as the domain is not available. As far as I know this computer was a WORKGROUP computer and not connected to a domain. Why would this start now and how can I recover. I have tried booting in safe mode and get the same response every time.