Thanks, I get the point, you are both right. Now I try to explain what I thought.

The problem was: if the video is interlaced, composed by two fields for each frame, 50 fields per second, then I must obtain a 720x288 50fps file... instead, I obtain a 720x576 25fps, THEN VirtualDub MUST do some kind of deinterlace... infact, I scan the captured video frame by frame searching for some kind of interlace artifacts, and because I didn't find any, I thought I was right (VirtualDub do some deinterlace).

After reading your comments, I rethought about the film and video difference, so I wanted to make another test... this is the result I wanted to see before:

So VirtualDub just take the odd lines from a field, then the even lines from the other, and form a complete frame without any deinterlace! Here the interlace shows up because this is a video clip - shot interlaced, not progressive... I was wrong because I didn't find any frame like this in the Star Wars captured video, just because as film originating material, the capture results in perfect progressive video!!!

I solved the problem, and I'm starting to remember I've done the same more than one year before, just I forgot... I told you, I'm going TOO old! ;-)

Thanks you Moth3r, thank you OmegaMattman!