I\'m not exactly sure how to do it... but I think it\'s something like this:
For Windows 2000 (sorry, it\'s what I use)
Start --> Settings --> Control Panel --> Users and Passwords
Uncheck the box near the top that says "Users must enter a user name and password to access this computer."
If you\'re using Windows XP, check out this site.
http://www.theeldergeek.com/automatic_logon.htmI\'d recommend downloading Tweak UI if you can find it. It\'s a great little program that will allow you to disable the logon without editing the registry in Windows XP. I use Tweak UI with Windows 2000 to disable logon.