1. First open your Capture.avi in VirtualDub.
2. Press the expand to fullscreen button on to top right of VirtualDub.
3. Right click on the left video plane and select 25% scale.
4. Right click on the right video plane and select 150% scale.
5. Go to the menu Video>Filters... and add "resize", select the size to be 512 x 384 with "Nearest neighbor" (this is only to aid finding the pulldown cut-off sections easier), then press OK & OK to exit the Filters... section.
6. Go to the menu Video>Compression... and select a fast compression codec, personally I use an MJPEG codec for this bit because each frame is a keyframe.
7. Go to the menu Video>Frame Rate... and select "Reconstruct from fields - manual", Offset: 0, select "Invert polarity", then press OK.
8. Go to the menu File>Save as AVI... and select a filename such as CaptureTest-0i.avi (0i because you selected Offset 0 with "Invert polarity" in step 7).
9. Keep an eye on the right video plane and as soon as you see the interlace artefacts (the 512x384 Nearest neighbor scaling makes this show up like a sore thumb) press stop.
10. Open the CaptureTest0i.avi in another instance of VirtualDub and scan through until you find the first frame where interlacing artefacts show up, if the interlacing artefacts start at the beginning then go back to step 7 and try Offset:1 "Invert polarity", then Offset:2 etc. until the start of the CaptureTest avi doesn't show any interlacing artefacts.
11. Once you have a section of test video with no interlacing artefacts go back to the first VirtualDub, menu Video>Direct stream copy, make the start selection at the start of the video and the end selection at the interlacing artefact frame of the 2nd VirtualDub.
12. Go to the menu File>Save as AVI... and select a filename such as Capture01-0i.avi, 01 for the section number and 0i or 1i or 2i for whatever pulldown setting you used.
13. Go to the menu Video>Full processing mode
14. Press Del on your keyboard so this will remove the video from the timeline and you can go back to step 7 to repeat the whole process again until all of the Capture.avi file has been split up into separate files each with their own 3:2 pulldown removal setting in the filename.
15. Now you've found the 3:2 pulldown removal setting for the individual avi files (if you're lucky you'll only get a few files) you can then process each one with your cleanup/crop/resize/whatever VirtualDub filters and save as say Complete01.avi etc. and join them all together afterwards (Append AVI segment... should do the job, some mpeg encoders can use a list of avis to create a single mpeg file so you don't have to join the avis up beforehand)
This was all typed out from memory so sorry if there's any errors in the process, it should work for you.