Well, this is relatively easy if you are into these kinds of things but probably too hard for someone who doesn't know much about encoding video.
Basically, what you do is this:
1. Export from camtasia as .avi with mp3 sound and 5 fps
2. Use
Avisynth and create a script like this:
<font class="small">Code:</font><hr /><pre>Video = DirectShowSource("C:\your\file\path\yourvideo.avi" , fps=5)
Black = BlankClip(length=numberofframesofyourvideo, width=120, height=80, fps=5, color=$000000)
return Overlay(Video, Black, x=300, y=240, mode="blend", opacity=1).ConvertToYV12()
# size and position of the black clip ofc have to be
# correct for the position of your name
</pre><hr />
3. Use
Virtualdub to compress the avisynth source into an xvid avi.
I can also do these things for you if you supply the file. PM for details.
Edit: You can do multiple overlays to cover up title bar and chat window as well. Just takes some experimenting with the correct x/y values to get them to the right positions.