|It means your hard drive is liable to fail at some point in the near future through wear-and-tear. All hard drives will fail eventually, which is why it is essential that you always keep backup copies of all your personal files (documents, music, pictures etc) on a different hard drive or on CD/DVD discs.|
if you don't have any backups, do it now before it's too late!
Then replace the hard drive with a new one. Don't ignore the warning, it will only get worse over time.