In TestStand or FlexStand select: Configure -> Station Options…
Find the User Manager tab and check the “Automatically Login the Windows System User”.
With this option checked TestStand uses the Windows username to login, without prompting for password.
If TestStand does not find a user by that name, the common TestStand Login dialog is then displayed.
Note that TestStand username must match the windows username exactly.
Additional information
Path to the Users file: <TestStand Application Data>\Cfg\Users.ini
For example: C:\Documents and Settings\All Users\Application Data\National Instruments\TestStand 4.1.1\Cfg\Users.ini