I have a laptop with W8.1, (Inspiron 3543). I have upgraded to W10 and returned to W8.1 after a while. However many preinstalled Windows apps like calculator, calender did not show up or opened. Some can be downloaded over again but more cannot be installed because it says they are already installed. İn these circumstances , as if I am forced to upgrade W10 that I disliked. Please Help! I want to use the system with W 8.1.