You just got a brand new PC with the latest Windows and you are amazed how fast it runs. Then you start adjusting Windows properties and installing programs that you need. After a while your computer is complete. Everything works, all operations are fast and you focus on your work. A common observation after a year or even before is that the computer is not as fast as it used to be. You start thinking what could be wrong. The hardware hasn't changed so it seems that some component is causing trouble. You go to BIOS settings only to confirm that all parameters are at initial values and nothing has been changed. But it is pretty obvious that programs start slower, opening and saving larger files takes a lot of time and with some operations you are getting annoying messages. It is very likely that the PC hardware is still working as it was when the computer was new. The problem is with the operating system.