Computer builders usually buy a smaller hard drive for the Operating System with high spindle speed (10,000 RPM), and a 1 TB (Terabyte) hard disk for storing photos, software, video and other stuff. Tip: Some people prefer the Western Digital 150 GB VelociRaptor SATA 10,000 RPM for Windows 7 Operating System. Some people like a Seagate Savvio 10K.3 300 GB 10000RPM 6-Gb/S SAS 16MB Cache (more expensive in the $230s), and others prefer the even more expensive and faster non-spindle SSD drives for Windows 7 Operating System. Use the horizontal/vertical scrollbar and type the brand or model in the store search box.