If the resolution of what you want to record is low enough, VirtualDub works pretty well. Just set it to capture a certain area of the screen and position the window for the game you're playing into that area. You'll also need to select video and audio codecs that can encode in real-time and configure them to do so.
Also, with any program that captures AVIs, make sure you select a CBR audio format since VBR audio doesn't sync nicely in AVI files.
--- Kris Asick (Gemini)
--- Pixelmusement Website: www.pixelships.com
--- Ancient DOS Games Webshow: www.pixelships.com/adg