So once I pressed update in Windows Update, and the progress bar appears and it starts updating. However, it got stuck in "Preparing Update Installation". I cannot press cancel because it says I need to be logged in as administrator which I am, but for some reason it thinks I am not. I tried rebooting the computer but it still stuck at the "preparing update" step.

Translation: "You must provide system administrator permission", "In order to cancel, you must be logged in as an administrator account, or request a system administrator to cancel."
How can I cancel it and restart it? I am using Windows 8. (Not Windows 8.1)