S3 How he solved hang prob. - while in Windows update

First time it happened, I brought the S3 to Acer Singapore service centre.  Problem: the unit could not boot.  The service man did something on the spot and it booted to last windows(restore?) before the update that hung the system. So no service was done.

Recently, the system was updating (same update) and again hung the system.  Again I tried reboot and it could not boot.

Question: How did the serviceman manage to reboot the system back to last restore point without usb.  I would like to reboot to the last working windows and backup some important files before doing factory reset or something.