Solid state drives (SSDs) are capable of delivering outstanding speed. So why don't they always do it? Why does the speed of a new laptop or netbook degrade quickly during the first months of use? It's because most PC operating systems have logical files that were designed for hard disk drive (HDD) use. They really aren't optimized to exploit the potential of SSD or NAND Flash. For these devices, drive performance falls off dramatically over time, and the main factor at work is fragmentation.