If you have used the secure logon method, that is the login without the welcome screen in Windows Xp (similar to windows NT logon), then by default you will be able to see that when you login, the last user who has logged in the computer would be displayed in the user name text box of the secure login window.
Some people might not like this as this gives away their user name.
To prevent windows Xp from displayng the username of the last logged in user in the username textbox, follow the following steps:
Open the group policy editor.(start > run > gpedit.msc).
Open Computer Configuration > Windows settings > security settings > Local Policies > securioty Options.
You will be able to find an entry called Interactive Logon :Do not display last User name.
Right click the property and select properties.
Select the enabled radio button and click ok.
Restart your computer.
Now you will find that the username text box is empty and does not contain the user name of the previous logged in user.