USERNAME Environment Variable May Differ from Actual User Name

When you log on to a Windows 2000-based domain, it is possible to use a logon name that is similar to the one that is stored in Active Directory. This may cause problems because the USERNAME environment variable is set to the user name that you typed in the logon dialog box, not to the user name that is stored in Active Directory. If any logon scripts relying on this variable, they may run up with unpredictable results.

A possible workaround to avoid this problem is to log on by using the user principal name (UPN) format. Instead of typing the user name, password, and domain on separate lines, type the UPN logon string in the User Name box. The UPN format is: Or, you can write a small program or batch file that resets the USERNAME environment variable to the value you need (you can get the actual user name with the Whoami utility) and add it in the Startup group.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.