CamStudio won't record?

I just downloaded and installed it and pressed record and it keeps telling me it can't record. Did I not install correctly or is there some other problem? I am not computer savvy so am unsure what I am supposed to do. Also is it possible to add audio later or maybe a written explanation?

That message sounds like you don't have am AVI codec. You have to install both the program and the Lossless Codec from the site below.

http://camstudio.org/