I can not get past the log in screen In win XP

I can boot up to the log in screen on WinXP Pro Sp3, but I do not get any user accounts. I have tried Normal Boot, SM W Networking, Command prompt, and Last Known Good. But I do not get any users on the log in screen. I do not get administrator in SM. Will a System restore, from CD work?
Booting to another HD, allows me to see the full file list so the data is not gone, just the Win XP User table or so it seems. I can not bring up Task manager or anything on the log in screen.