First check in the Hardware Compatibility List for Backup Exec 9.1, if your robotic library is supported. You should have the device and drive manufacturers and model names:
http://support.veritas.com/docs/282347
Then check in the Device Manager in the Windows Operating System, if your device shows up as installed.
Then check if you have the latest drivers installed. For the latest drivers:
http://support.veritas.com/docs/273853
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