ahhhh chr*st! Just put it in, held down the volume up button and then the power button, it said "Okay, push any key to reboot", and then it started beeping maniacally and now says "Update has been cancelled! Press any key to reboot"
Walking slowly away from the computer now, swear I'm ready to fling this right back to astak but I'm too stubborn and insist on torturing myself to find the answer

Must eat cupcakes