Windows 7 update frozen?

Should I just let my computer's battery die, and then try and re-boot? I have windows 7. It was performing a system update and said " Please do not power off or unplug your machine. Installing update 1 of 1." Well my little brother turned off the computer, causing that page to freeze. The mouse is still showing the spinning wheel, but I can't move it. I tried re-booting but no luck. What should I do? Do I need to hold down the power key longer? Im pretty sure pressing certain keys won't do anything because its been frozen for hours. I would appreciate some serious suggestions. Thank you. I am on the internet on my phone now if anyone is wondering.