All Macintosh hard disk drives contain a small partition containing low level drive support code that are loaded into memory at start-up time to support the functions of the hard disk.
If your hard disk does not mount on the desktop normally, updating the driver with a formatting utility, such as Drive Setup or HD Setup from Apple, may be the solution.
You are strongly encouraged to run Disk First Aid (or equivalent 3rd party utility) before updating the hard disk's driver. If the utility program cannot repair the damage, then update the driver. Updating a corrupted disk's driver could lead to data loss, so backup all data before updating the driver.
If updating the driver fails to correct the issue, then you may need to reformat the hard drive. Again, backup all data, as reformatting the hard drive will erase all data.
As a general rule, you should use the same formatting utility to update the drivers as you used to format the disk originally. If you are updating drivers with a different utility, you should backup existing data when possible and consult the vendor of the new utility to see if their new driver can safely replace the old drivers. Drives with multiple partitions could be at risk of data loss.