Startup Problems

• Computers with failing or completely "dead" hard drives often experience problems when starting up. Rather than starting up as expected, they may start extremely slowly or refuse to start up at all. In many cases, these events cause an error to be displayed on the screen, such as "Hard disk about to fail" or "Windows could not start because [a reason]."
  
  

Unexpected File-Related Errors

• Computers with hard drives that are about to fail may display error messages related to the file system during normal usage. Error messages indicating that files do not exist or are corrupted aren't necessarily related to a hard drive problem, but if they begin to appear frequently all of a sudden and without any obvious cause, the problem is probably related to the hard drive.
  
  

Strange Behavior

• A computer with a failing hard drive may begin to act strangely all of a sudden. Many programs may crash at once, or the computer may experience a serious error and then refuse to boot up again. Such behavior can be caused by other problems, such as computer viruses, but may also be caused by a hard drive that has failed or is about to fail.
  
  

Anomalous Noises

• Some computers produce a slight noise when accessing the hard drive. If something is wrong with the hard drive, the noises may change. They may become louder or faster, or they may stop entirely and abruptly.
  
  

Drive Warnings

• Finally, some computers use a technology called S.M.A.R.T. (Self-Monitoring, Analysis, and Reporting Technology) to attempt to detect problems with the hard drive that indicate it is about to fail, such as mechanical wear. If a S.M.A.R.T.-equipped computer detects that its hard drive is about to fail, it can warn the user of this so that the data on the disk can be backed up.