If I were you I'd REALLY do a backup if you still can read it...
Then if its already failed but you did not make a backup, there is several tools you can use to recover parts of the info, assuming the HDD is not totally dead, from an electrical or mechanical point of view... Trying to recover data using recovery tools, you will experience variable degrees of success. Dont imagine it is like copying from a functional drive.
If you are comfy with Linux, you can try testdisk a& photorec. dd would work as well, but be VERY cumbersome to get the files (create an image, mount the image, retrieve files, copy them somewhere else , etc)... If you need help with linux, let me know.
If you use Windows, I imagine there are tools as well, but you'll have to pay.
Always have your data at least in 2 independent medias. 1 hDD + DVD's, 2 HDD's, 1HDD + USB drive, etc..... I myself have 4 backups of my critical data. I've lost everything too often not to become paranoid on computers