XP doesn't recognize my external 500 GB WD My book... I tried to plug in my brand new Western

Question

I tried to plug in my brand new Western Digital My Book 500 GB external hard drive today and when I did I received an error message stating that the USB device has malfunctioned and XP is unable to recognize it. Am I doing something wrong or is this a bad unit? Someone told me that I might need to install drivers but there were no discs with the unit, and it says on the box it is plug and play. I am confused and would appreciate any help I can get. Thank you my 320 gb will not hook up to my windows xp