.net doesn't directly support video formats. Your best option would be to use a 3rd party tool to generate the .avi.
ffmpeg is one option. You could access it directly via a command line like this:
ffmpeg -f image2 -i img%d.jpg /output/a.mpg
You would need to name your images img1.jpg, img2.jpg etc. For more details see the ffmpeg faq. You should also find details in the faq for how to output different video formats.
You can start a process from vb using Process.Start(). Something like this:
Process.Start("ffmpeg.exe", "-f image2 -i img%d.jpg /output/a.mpg")
You could also take a look at ffmpeg-sharp or Tao.FFmpeg, they are .net wrappers for the ffmpeg libraries. I haven't tried either personally, but it looks like it might help you out.
Another alternative would be to take a look at MEncoder, which has similar functionality. You should be able to look up a similar command line for this tool.
[Related SO question: 271003]
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…