WD  Caviar Green 640 GB SATA Internal Hard Drive Retail Kit - WD6400CSRTL Massive capacity - Capacities from 500GB up to 2TB offer the most available capacity for storage-intensive programs and space-hungry operating systems, like Window Vista, with plenty of room left over for photos, music, and video. Reduced power consumption - WD has reduced power consumption by up to 40 percent compared to standard desktop drives with the combination of WD's IntelliSeek?, NoTouch?, and IntelliPower? technologies. Caviar Green drives yield an average drive power savings of 4-5 watts over standard desktop drives making it possible to build systems with higher capacities and the right balance of performance, reliability and conservation Cool and quiet - GreenPower? technology yields lower operating temperatures for increased reliability and low acoustics for ultra-quiet PCs and external drives. IntelliPower - A fine-tuned balance of spin speed, transfer rate and caching algorithms designed to deliver both significant power savings and solid performance.