Well, there's two methods (there's more, but these are the most used ones) of record movies in AVI, MPG etc.
The first one is to use the ingame method to record a lots of screenshots (cl_avidemo).
The other one is to use a 3rd-party program to record with. For example
Fraps
Using Fraps is very easy and gives a good result. But the filesize gets very big when you are recording with Fraps, so you need to compress it with Divx/Xvid or another codec.
But for the first method (cl_avidemo) you need to spend some more time, but the result is better (I recommend using this method).
When you are watching your demo with this command set to 30, a lot of .TGA files will be saved in your Main/screenshots folder.
You need to convert them to .JPG files. Use
Reaconverter Pro for this job. (If you dont want to convert 5 files in a row, PM me and we will sort it out

)
Then you got a bunch of .JPG files, and you need to put all of them together in a moviefile. Use
JPGVideo for this job. After you got the moviefile, you can edit it in whatever edit-program you like, such as Vegas, Premiere, Avid FreeDV etc.
Some useful links:
Avid FreeDV
Sony Vegas trial
Reaconverter Pro
JPGVideo
Fraps
Hope this helps
