WD My Passport Partition Error Message

Hi there,

So my WD My Passport device was working perfectly fine about 20 minutes ago, but I had to go somewhere so I locked my Computer. When I came back and tried to unlock my WD device, the unlock window wouldn’t even show up. I got that part fixed but when I unlocked it it still didn’t show up on my “My Computer” screen. I then recieved a message that reads as follows:

Since I’m a total n00b, I have no idea what it’s talking about. My drive is unlocked, and I’m fairly sure it was formatted for Windows Vista. I have a whole ■■■■ ton of important stuff on that hard drive, so does anyone know how to fix this? 

P.S. When I check under “Disk Drives” in Device Manager, it says the device is working properly. I don’t understand this.