I wanted to do a Let's Play for YouTube (of SSI's Curse of the Azure Bonds) with narration, and hadn't yet figured out how to smoosh together a separate narration track (from Windows Sound Recorder) with DOSBox's native video capture. (My teen daughter, who posts occasional music lyrics videos on YouTube, thought it could be done in Windows Movie Maker, but hadn't yet made the attempt.) Another YouTuber who does Let's Plays of Gold Box games (aulddragon) referred me to a how-to video on the subject by Lateblt, which helped a lot. Both of those fellows use CamStudio to record gameplay & narration in a single step. (CamStudio 2.0 is quite stable, so that's the version I now use.) After recording a gameplay session in AVI with CamStudio, I convert it to FLV with Any Video Converter (there are other converter programs out there, but that's the one my daughter's been using, and it's easy for me to use, too), then upload the FLV version to YouTube.
Now if I could just get rid of the slightly-delayed "echo" of my voice through the speakers when recording! It doesn't show up in playback, but it's annoying, and throws off the pace of my narration. 😅