Whether or not you're on a local area network, odds are you don't really need the little logon (login) screen asking for your username and password that comes up when starting Windows. To remove this prompt, follow the following directions: -
Windows XP - solution 1:
Select Run from the Start Menu, type control userpasswords2, and click Ok.
Turn off the Users must enter a user name and password to use this computer option, and click Ok.
Windows XP - solution 2:
If you have one user account and no password configured, Windows XP will log you in automatically. Otherwise, you'll have to do the following:
Obtain and install the Windows XP version of TweakUI. Open TweakUI (it's in Start -> Programs -> Powertoys for Windows XP). Expand the Logon branch, and click Autologon. Turn on the Log on automatically at system startup option, type your username and password, and click Ok.