Problems with "My Book Essential 2TB"

I am having various problems with “My Book” sometimes it doesnt appear on my PC, sometimes it appears on the PC as Local Disc but no access is available, sometimes it appears and access is available but its very slow. I have tried it on another pc  and it was slow on it, can anyone help?

Use checkdsk or other utility to test the drive

It looks like it’s about to die for good

backup all data ASAP