Download CamStudio 2.0 (here) and the CamStudio Lossless Codec (here) and get them installed on your machine (time required: 5 minute download, 5 minute install).
Many of our screencasts here at ShowMeDo are created with this wonderful (and free!) package. CamStudio lets us make perfect-quality videos of our Windows desktops.
You need both the CamStudio exe and the Codec zip file. Install the exe in the normal fashion. To install the Codec you'll need to unzip the zip file then right-click on camcodec.inf and select 'Install' (you need Admin rights to do this).
CamStudio is open-source and free to use for commercial and non-commercial videos. Background: screencasting, loss-less compression, sourceforge download page, Nick the Geek's camstudio.org.