I was having a root in there yesterday as I have been having a problem and thought maybe something in the settings have changed and noticed Secure boot. I know it was not in there before, so it must have been added on the update. I did not think it could be added and was built into the hardware, but it seems like I was wrong.
I have no reason to switch it on, just surprised it was there.
i still did not sort my problem out, may be a restore from my backup is needed.
Desktop machine now powered by windows 8 pro 64bit, no dreaded metro and Linux , laptop by Linux