1. Blue Screen of Death - Memory dump screen, usually its bound to some file system corruption or hard drive errors.
2. Slow Access of data - Opening of a regular file which would usually open fast enough is now taking a lot more time. Technically, most of the times its due to bad sectors.
3. Time to Boot Increases - System boots up really slow.
4. Drive making sound - When the drive is in use and if you hear any sound or intermittent clicking.
5. Hang - The system gets hanged / freezed quite often.
When you experience any of these make sure, you start taking a backup. And look fo a new drive to continue working.
