Western Digital Elements 640GB 2.5″ USB Portable Drive for $59.99 shipped after coupon code BT?BG87Z21PJW9. Here is a screenshot for your reference. Note that the coupon code expires after 1000 uses. This 2.5″ portable USB drive does not require a separate power supply and is smaller than most external drives, making it much more convenient. Most places have this portable USB-powered 640GB drive for about $84 or more.