I can only login as "Administrator"

I think you mean welcome screen.

See what users are under documents and settings on the C:\

http://support.microsoft.com/kb/291559

To configure Windows XP to use the classic logon and shutdown screens for every logon session, follow these steps:

1. Click Start, and then click Control Panel.
2. Double-click User Accounts.
3. Click Change the way users log on or off.
4. Clear the Use the Welcome screen check box.

Note If you turn off the Welcome logon screen, you also turn off the Fast User Switching option.

Turn on automatic login XP

http://support.microsoft.com/kb/315231