Reboot or Not to Reboot?

Why and who can request to restart your PC? Why can my application cause the system restart request? How to avoid system restarting if your application causes that? How to detect that hardware used by your application is about to be removed? Is that possible to do in the system service as long as in regular application? What if such things are necessary in the kernel mode? How to detect that new hardware with the type which you are interested is plugged in or unplugged? That is all the aspects and even more interesting system things are covered in this article.