External HDD not detected in my laptop – XP

I have recently bought a 120gb seagate External HDD. I have been told to just plug in and use the storage device. But the system is not recognizing the device. I tried restarting the system, plugging in and out and various combinations of the usb ports given. It is a 2.0 usb cable. I have XP running on my laptop

Can anyone please help me out on how to solve this problem??????