My Book 1TB External Hard Drive will not open, or opens extreamly slow

Recently my 1TB External Drive has not been opening like it once had. I believe it has been about a week since this started to happen. I will open My Computer and double click the My Book drive and it appears as though it is going to open (hour glass shows for loading) but it takes a long time for it to open and when it does I can’t really open anything from it. So I am forced to close it. After it closes my desktop refreshes and goes back to how it was prior to trying to open the my Book drive. I have checked my drivers to make sure they are working (they are) so its not a problem with the driver. I have tried to run the diganostics test that is installed on the hard drive and it failed. Both the full and quick scan failed. If anyone can help me with this problem, let me know.