Can anyone help with this a USB problem?

For months I've used a USB External HD. Now when I turn on my HD XP flags me with "Unknown USB device. USB has malfunctioned.."

How do I fix this.

I've tried to update drivers in Device Manager, but nothing works. HELP!!!!

Have you tried disconnecting the HD from USB,and then removing the USB controllers in the Device Manager,and then shutting down the PC,connecting the HD,and then restarting.Sometimes works.Sometimes doesn`t.