If you set up a user account without a password, and then attempt to log in across the network. By default, Windows XP doesn't permit remote users to connect from the network without a password. To allow access without a password:
Go to Control Panel | Performance and Maintenance | Administrative Tools | Local Security Policy.
Expand Local Policies | Security options.
Double-click Accounts: Limit local account use of blank passwords to console login only, which is enabled by default. Disable this option
