This happens only when the drive has been formatted with the Internal HD Format program included on 580 Series, 630 Series, 5200 Series, and 6200 series computers. (For a list of computers with IDE drives, see the article titled "Macintosh Desktop & PowerBook Computers: IDE Hard Drive" in the Tech Info Library.)
The solution is to back up the hard drive and reinitialize (low level format) it with Drive Setup 1.2.2. Drive Setup 1.2.2 is located on the Mac OS 7.6 CD-ROM in the Utilities folder. Note that reinitializing will result in the loss of all information on the hard drive, so performing the backup operation is critical.