Hello,
Please verify that the drive is detected by the Windows Operating system.
Backup exec will not recognize the external B2D as a storage device but has to be configured with removable backup to disk folder.
You can use external B2D with BackupExec as a "Removable Backup-to-Disk" folder.
Please ensure that external B2D appears as a drive letter on your system
Please see the technote for more information:
http://support.veritas.com/docs/253764
Thanks,