Windows Movie Maker used to come pre-installed on Windows but no longer does. Microsoft has stopped supporting it and making it available. If you still have access to it, however, it is a solid basic video editing tool.
Free screencasting software that works from your browser. You can make an account, but you don't have to. You can make a video and publish it immediately to the web or download it and edit it further. Free accounts will include a watermark in the corner of the video.