Cannot WD External Hard Drive

Hello,

I have a WD external hard drive that is full of important information and was working perfectly until yesterday.

Now, when I connect it to my USB port, it lights up, but I cannot find it in My Computer. I know the computer has recognized that something is attached, because when I go to the disconnect icon in the bottom right, it says "disconnect USB mass storage device", but I cannot find it anywhere else.

Any help would be really appreciated, as I'm traveling and the info is vital.

Thank you very much!