Computers have nothing to do without their operating system and software. Since almost all of that is stored on a hard drive or solid-state drive, the drive's performance greatly affects the overall performance of the computer. While the files are being read, you're waiting. The performance of the drive determines how long you wait. Hard drives have moving parts, so you're waiting for the drive heads to move to the right track and read the data as it goes past them on a spinning disc. File fragmentation causes hard drive heads to move around a lot, picking up the pieces scattered across the discs. Solid-state drives have no moving parts, so not only is the performance higher, but you don't run the risk of mechanical failure. They also use less power and generate less heat, reducing the need for cooling in a computer and extending a notebook's battery life.