Green light blinking and the hd drive cant be found by the system

I have a western digital mybook 500gb external hard drive

when i opened my pc the system didnt find the hard drive and I noticed that the drive’s green light was blinking.

the light blinks even when I have the pc shut

I run windows vista

I unplugged the hd for almost a day and nothing happened. still it was blinking and the system couldnt find it

please can anyone help me?

check to see if the drive shows up in disk management.  you can also look at this kb article