This things happened in my computer. Make sure if your computer have a virus. It causes by some kind of virus because it eat/waste the core/system file of a computer. Or it can be happen if you have a antivirus in your computer. In some cases antivirus block system files of a computer. Then you should reinstall windows in your computer. Maybe it helps. If not then take your computer to a computer hardware store to find out what is the problem. Thanks.