I found this on google, hope it works. BTW, review the file for dodgy functionality...
quote:
From http://www.dougknox.com/xp/scripts_desc/xp_hide_users.htm
This VB Script will allow you to hide users on the Welcome screen.
To use: Download the xp_hide_users.vbs file and save it to your hard drive (you may want to right click and use Save Target As). Double-click the xp_hide_users.vbs file. You will be prompted when the script is done.
If you hide an account, you can access it from the Welcome screen by pressing CTRL-ALT-DEL twice. You'll get the older style logon dialog. Type in the username and password.
To unhide a user, and make them show up on the Welcome Screen, download this script.