AVIScan
A small console tool I wrote that scans AVI files using FFMPEG to guess at whether they're valid. Very much an "alpha" tool, as I stopped developing it as soon as it worked.
Usage
Build in VC#.
Run from a command line, specifying the folder to be scanned as an argument. Example: aviscan "C:\videos"
Generates a log file in the aviscan.exe folder with the same output as what is printed to the screen