There is hardly a problem with adding a new hard drive to a desktop computer but how should one update the hard drive on which the operating system is installed? Hard drives fail, I have experienced only one over a period of twenty years and that was replaced under warranty! Even though it was not very old, of course. So protect your computer by replacing your hard drives. The problem is, how does one do that for the system drive? Most systems have OEM installed operating systems and have no discs -when bought used.