Hard disks come with different speed ratings, ranging from 4,200 revolutions per minute (rpm) to 15,000rpm. A common speed is 7,200rpm, which offers the best value for money. We've chosen a Western Digital GP Caviar hard drive, with a 7,200rpm speed and 500GB of storage. This hard disk can vary its spin speed, slowing down when the PC isn't doing much to save energy. For a desktop PC, a 3.5in hard disk is appropriate, but optic.al drives -a DVD drive, in other words measure 5.25in. We chose a Sony SATA AD-7190S¬OB DVD Writer that can play DVDs, as well as handling CDs. It can also burn CDs and DVDs. The same would cost you around Rs.l,700. However, there are various other brands like Samsung, LG, Asus whose DVD writers are equally good and can be purchased from computer retail shops.