You can download and install the Drivers from the following link.
VERITAS Backup Exec (tm) 9.1 - Device Driver Installer (20041101) - Includes Tape Driver Release (20041006) and Robotic Library Release (44) (Intel Only)
http://seer.support.veritas.com/docs/272474.htm
Refer the following Technote to install the Drivers.
http://seer.support.veritas.com/docs/199881.htm