First thing, BE 12.5 on Windows 2008 R2 is an unsupported installation. Next, In order to get it working with Backup Exec, first you would need to get it detected by Operating System. So, from disk management when it sees the drive, it will need to be initialized. When initialized, it would add signature to the disk. Then it should detect the drive letter and data should be read in windows explorer. Only then, would you be able to create a backup to disk device in Backup Exec software on new machine.
Please mark it a solution, if this is useful.
Thanks