Yeah! Phil22 is right! Every drive may die or fail someday. You should learn to keep your important data backed up at least on two different drives.
But, now, have you tried a diagnostic tool to check it? If not, you can run SeaTools for Windows: http://www.seagate.com/support/downloads/seatools/
For the data inside, you could try to retrieve your important data for free with the help of a free drive recovery tool. Actually, I have never tried it before. But, my friend has used it as his WD drive is inaccessible. At that time, I am there and prove the whole process. It is really trustworthy. Download it there: http://blog4mark.blogspot.com/2012/11/how-to-repair-cor...
Or you may prefer to consult a data recovery company.
I hope my information can help you.