Problem with ScanDisk

What does it mean when ScanDisk stops short, at, say, 176,332 of 2,512,036 clusters and cannot be induced to resume scanning? I’m running it on Windows 98 with Norton AV 2002 disabled. Does this mean the hard drive is shot? that the head-to-toe pointer chain is broken? The computer actually runs moderately well once I get it started, and the applications are evidently able to access parts of the hard disk which ScanDisk can’t. Also, what’s wrong with the hard disk? I don’t get a summary report. Thanks.