Can't login after switching from domain to workgroup

Hi,

I have a PC running Windows XP Pro SP3. This PC was originally part of a
Windows 2003 Server domain "OldDomain". When I got this PC, I was still able
to log to the PC in with domain credentials (username = "OldUser"; password =
"OldPassword")

My plan was to remove this PC from the domain and to put it into a
workgroup. I made this change and it worked just how I had hoped - the PC
was now able to share files with the small workgroup that I put it in.
Everything was great until I restarted the PC. Now, I am no longer able to
log in with "OldUser" and "OldPassword". Can anyone tell me if there is
anything I can do? Unfortunately, I do not know any other account / password
combinations that work on the local computer.

Any advice will be appreciated.

Thanks in advance,
Paul


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Paul Kraemer