it seems that I cannot save pictures with Vegas 4.0. Can you recommend me some cute and small tool, that can find matching half images in AVI file and same them as bitmap?
If it's progressive, shouldn't have but one frame rather then 2 field or halves, and Vegas does it just fine by clicking on the floppy icon above the preview window. This just takes a picture of the window however, so you want your video preview at full size.
Otherwise, you'll find a host of players at doom9.org & digital-digest.com. Many DVD players like PowerDVD also offer snapshots and will handle avi files fine.