ArcGIS Desktop 9.3.1 and ArcInfo Workstation 9.3 may be downloaded by any student, faculty, or staff for use on personal and university owned computers. There is no charge.

http://www.ncsu.edu/software/available-software/product.php?software=170

It's highly recommended to follow the installation instructions, which include the path to the License Server.

Be sure to also install the Service Packs!