It is no secret that when you purchase a new computer, laptop or tablet, it is virtually obsolete in a very short period of time. "Moore's law" is the observation that the number of transistors in a dense integrated circuit has doubled approximately every two years. There is debate as to whether this period is two years on the dot, or eighteen months, or accelerating or decaying, but one fact remains – it will not be long before you feel the need to upgrade your computing device.