It is possible to hide the user name of the last logged on user in the logon dialog box in Windows NT.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
Start Regedt32.exe and locate the following registry key: Add a REG_SZ value named DontDisplayLastUserName. Set the data value to 1 to enable the new feature. A data value of 0 disables the feature.

The Last Username Display can also be hidden without editing the Registry directly if you have the Windows NT Resource Kit.

1.	Click Start\ProgramsResource Kit 4.0
2.	Click Configuration\C2 Configuration
3.	Double click the line that reads "Last Username Display"
4.	Place a check in Hide the last username to login.
5.	Click Secure then OK.