To allow users to log onto their computers without a password and then access the XP Professional machine without a password, you must make a security policy change:
1. Go to Control Panel | Performance and Maintenance | Administrative Tools | Local Security Policy.
2. Expand Local Policies | Security Options.
3. Double-click Accounts: Limit local account use of blank passwords to console login only, which is enabled by default. Disable this option and click OK.