Tomas,
I’m not in front of Vegas right now, but, if you select the tracks you want to multi-cam edit, then go to the tools menu you should see (near the bottom) prepare multi-cam tack, or something like that. Then, select enable multi-cam editing. (Not sure on the wording) Look in the help system for details.
An AVI is a ‘container’ for a wide variety of video formats. You need to analyze with a utility like gspot.exe (available on the web) and locate the codec that was used to make the file. Beware, do not install codec packs, the will replace paid-for Sony supplied codecs with free or hacked codecs, and your videos will be less quality. If you have codec questions ask here.
Jeff
http://www.narrowroadmedia.com