When you boot up a computer running Microsoft Security Essential, you may notice a "potentially unprotected" message until the software has had time to fully load and then check with Microsoft's servers to make sure it's up-to-date. (Its little Castle icon in the notification area will also be red, instead of green, while this message is being displayed). On a fast computer on a fast network this message flashes by so fast that it's often not even noticeable. However, on a slower computer and/or on a slow network, it can sometimes take a while for the software to get fully loaded and then check-in for updates.