Most webcam manufacturers include a CD with software, check it if you have it. Most of the times they include video recording software for that webcam. Please search the manufacturing website, or give me the brand and model so I can look it up for you.
If you cannot find any of these things, you can use Windows Movie maker for recording video. It sucks but hey it's something and it's free. I would really recommend however finding the software from the manufacturer, simply because it usually enhances the camera's performance.