How do I get my computer to recognize my external hard drive ?

i’ve had this freeagent seagate desktop external hard drive (250 gb) for little over 4 months. Now suddenly since yesterday it just stopped working and my computer doesnt recognize it at all. I’ve looked in other forums and places and still those methods dont work. It just doesnt seem to recognize it. My flash drive 1gb works and other devices that use the USB port seem to work, just this one is an exception.