Why was Windows Advanced Server notable?

Windows Advanced Server was notable because it represented a significant evolution in Microsoft's operating system capabilities, particularly in terms of architecture. This edition of Windows specifically emerged as one of the early implementations of a 64-bit operating system. The transition to a 64-bit system allowed for improved performance and the ability to utilize more memory than was possible with 32-bit systems, making it particularly beneficial for server environments that handle large amounts of data and require robust performance.

The other options do not accurately represent the key features or historical significance of Windows Advanced Server. While early versions of Windows did indeed support multi-user environments, this was a broader characteristic across many Windows releases rather than a standout feature of this particular version. Although advancements in mobile device design and graphical user interfaces (GUIs) are significant in the history of Windows, these facets are not what made Windows Advanced Server noteworthy among its contemporaries.