Thank you. All of you for your help. Yesterday I talked to a friend and he tell me to restart the iMac while keeping pressed the ALT OPTION key, I did this and its allow me to restart the mac in the usual way. I didn't think on this before.
My iMac does not want to start. Apparently my little kid was playing with the keyboard, and when I sit to work my computer ask me to restart it by pressing and holding the power button. And when it suppesedly restart only shows me a white screen. Any help will be appreciate it. Thank you. I...