This pop-up window appears whenever the server uses NTLM authentication. When navigating in the application normally (outside NeoLoad), the browser sends the encrypted authentication information to the server transparently.
The account used is the Windows account of the logged-on user. When recording, NeoLoad asks for an account name so that it can record and play back the authentication.
This credential are stored in the server definition under the "Design" section.
For more information, see "Authentication" under "Design" section in Neoload documentation.
