I have some unpleasant news for you, your hard drive is failing. This means that at any time, it would suddenly stop working, and all of your files and software would be lost.
I recommend that you backup all of your important data onto disks or an alternate hard drive.
I recommend that you read this link HERE
. It has a list of the best free backup software, which will make the process easier for you. On that link, I recommend WinBackup. If you would like to purchase backup software, I know Nero has an easy-to-use backup that can easily create disks.
If you need help with backing up your computer (it can be very confusing and difficult) I recommend that you go to either of these websites, TechGuyWhatTheTech
Register there and make a new topic in the appropriate forum asking about backing up and how to do it.
After you have your data backed up, you need to go to a computer store and buy a new hard drive.
When you replace the Hard Drive, you can use the disks to restore the backup that you make. You could also ask in the forums above how to do this.