From Apple Software Update:
The Hard Disk Update improves the longevity of some hard drives. Your drives may or may not need to have firmware updated; installing and running this update will tell you if updating is required.
IMPORTANT -- It is strongly recommended that you back up the data on your hard drives to an external drive or removable media before running this update. If an error should occur during the update process, your hard drives may become unusable. In that case, all data on the drives could be lost.
Note: When installation is complete, Hard Drive Update 1 should launch automatically. If the update does not launch automatically, please launch it manually:
/Applications/Utilities/Hard Drive Update 1