It looks like Microsoft has another prerequisite for installing Vista SP1 on a laptop. You have to have it plugged in to the AC adapter, or you cannot continue with the installation. At the moment, I had 50% battery life remaining, which was about 2 hours, and I attempted to install SP1. The message was: "Setup requirements" "Before installing Service Pack 1, plug in your mobile PC power cord to ensure that your computer maintains power during the installation." (See attachment for screenshot) I was denied until I plugged in the AC adapter. I guess it's kind of a smart idea. Running out of battery in the middle of a Service Pack install would NOT be a good thing!