Western Digital Caviar Blue 640GB 16MB Cache Interal Hard Drive for $59.99 Shipped

Western Digital Caviar 640GB 16MB SATA Hard Drive for $59.99 shipped.  Here is a screenshot for your reference.  It uses a high-density 2-platter design for better performance while reducing power usage.  Note that it comes in OEM packaging, which means no pretty retail box and marketing materials but is otherwise identical.  Most places have it for about $69.