|I had something similar with my computer, when I added Novell by mistake. The default entry was the computer name and/or the last user name on the PC, without any password. I think I looked up Novell documentation to learn about this default setting. You might want to try this approach and ask the person who sold it if they know the computer name and/or any user names that might have been in use. I think MS Windows will default the user name to something like "Owner".|
It's not much, but if formatting means losing programs that might be on this PC, it might be worth a little poking around.