Harddrives have a feature called SMART which monitors a plethera of parameters like read and write errors. If values reach a threshold it will trigger this kind of warning. One way to take a look at that is the SMART-Monitor of PartedMagic, a free linux. Backup often and replace soon.
Your hard drive has crashed. Hopefully you might be able to recover your data but most likely not. You can reinstall windows hopefully or you may need a new one.
It is likely that the hard drive contains 'SMART' technology that monitors for read/write failures along with other hard drive error conditions. If certain error thresholds are exceeded you will be warned that a failure is imminent, so you can back up data before it fails.