Modern hard drives have a feature called 'SMART' which stands for 'Self-Monitoring and Reporting Technology. They are able to send a message to the screen to let the user know whether the drive is still healthy or is starting to fail. I can't vouch for how accurate this technology is, but you would be well advised to at least back up all your own files which are on that drive as soon as possible. If you know the make of the drive, most of them have a utility you can download from their website to check the drive with a special boot-floppy. This will confirm if the drive is healthy or failing. My guess is the message you are getting now is correct and you should fit a new drive as soon as possible.