By default windows XP doesn’t show the Administrator in the user list at the welcome screen. This simple trick lets you just display admin account at the welcome scree.
Here’s a way to get around it.Just follow the simple steps.
Now head up to HKEY_LOCAL_MACHINESoftwareMicrosoftWindowsNTCurrentVersionWinlogonSpecialAccountsUserlist
create a new DWORD entry and name it as Administrator and change its value to 1.
exit and reboot for the changes to take effect.
To change it back change its value to 0 or simply delete the key.