My WD digital external hard drive doesn't show up whenever i connect it to any sorce..?

i have a western digital 320 gb harddrive.. and just yst i connected it to my laptop and it shows its connected to the laptop at the notification area but doesnt auto play or show the icon in my computer.. i then took it and connected it to my playstation 3, it still didnt show.. whats wrong.. i didnt format it ot anything.. just out of the blue.. i really have some imp data in there.. how do i get it back..