Frink, thanks for getting back to me. I've spent the last few days playing with Womble, which I've used to make my fan edit, but it's very rough, because Womble's rough, and I'd like to redo it using Serif or Movie Studio Platinum, if I can get either to work for me.
About virtualdub . . . maybe the copy I have is corrupted or something, because it won't open m2v's or anything else.
Serif I can get to work some of the time. I have to use pgcDemux to separate the audio and video, then recombine them in Serif. This works well for The Hobbit: Parts Two and Three, but it doesn't work for Part One. The audio and the video won't sync up for some reason.
Movie Studio Platinum is a great editing system, but it only seems to want to open MP4s properly--that is, with audio and video synced. I try to remove the audio and insert a different version of the audio track, and it's still not synced. And I can't seem to get MP4s in a high enough quality to use. Not sure what to do.