OK. Firstly make sure Removable Storage service is set to disabled, and not running.
Check to make sure that your device is using the Veritas drivers, and if necessary, reinstall them.
If your SCSI is out of the server, your drive is not attached. Then I'd suggest the following:
1. Open up Backup Exec, and remove the drive. Run the wizard to remove all device drivers if this allows you to do this. Remove the device out of Windows.
2. Shut down your server, put in your SCSI card, and connect your tape drive.
3. Start up your tape drive, give it a couple of seconds, and then start the server.
4. Windows should now redetect the device. Run the Device Wizard, and reinstall the drivers.
You can also check your Event Viewer for any errors, pointing to a device problem. These should be in the System Log, and are Error 3, 7, and 11 (if memory serves me correctly).
LASTLY...to make sure it isn't a hardware issue, stop your Backup Exec services, and then try NTBackup. Don't forget to start up Removable Storage service again.
