When attempting to map my workstation to my server, why am I asked for a username and password?
If password-protected sharing is turned on, the person with whom you want to share a folder on your computer must have a user account and password to access shared items. When you attempt to access a password-protected shared folder you will be presented with a request for a user account and password for the computer on which the folder is stored.
Generally, password-protected sharing is turned on by default. For more information, see the Microsoft website.
To resolve any issues with password-protected sharing, especially when mapping a network, please seek assistance from an I.T. professional or your administrator.