|.SWF's are compiled (like applications), .AVI's are movies only. |
I.E.: an SWF may contain multiple movies, multiple pictures, and application code to handle what loads when...you can't just "convert" it to an AVI...
Here's some good free SWF manipulation tools:
There's a program for going AVI->SWF, but not the other way.
To do SWF->AVI you'd need to use SWFExtract and (hopefully) it will dump out media files (flv maybe), that you can convert to AVI.