In Windows 2000 Home and Professional, you can use the following setting.
Start, Settings, Control Panel, Users and Passwords, select the desired user, and uncheck the box above the user list: "Users must enter username and password for the computer".
This works only for local logons, not when you log on through a domain.
For Windows 2000 Server this setting does not exist. You can either find out about the required settings and put them into the registry directly, or you can find and use TweakUI.
For more information, please see the Microsoft Knowledge Base article, "How to Enable Automatic Logon in Windows 2000" at
A word of warningwhen you enable autologon, the password of the user that is logged on automatically is put in the registry as plain text that can be seen by anyone who can get access to the computer. Don't use autologon if this is too risky.