You just might have a big problem there. Ever seen a TV or movie screen than it was taller than wide? I don't shoot video & therefore haven't done any research on software for editing but what you did may take some work to salvage.
Please take the time to let us know any results. In my head I see each frame as a portrait style photo & my thinking is that in order to change it to landscape mode it's going to need to crop out part of every frame to resize them for display on either a TV screen or computer monitor. Whatever you do make a back up copy before modifying the original.
I'm using Windows Movie Maker. I've already turned the file around but it has a large section on both sides that is black with the picture in the middle. I'll have to see if MS Movie Maker will carry out your instructions. Thanks. I'll let you know how it comes out. I've saved the production by Movie Maker, made a second copy into another format since the Windows' format wasn't compatible with the players I have. Now, I'll see if I can crop and resize.
See "Vertical Video Syndrome": http://www.youtube.com/watch?v=Bt9zSfinwFA
All in fun, of course. But the point behind the video is real. Camera's wont flip the video the video on it's side to correct. When shooting video, always hold the camera level (horizontal) and not turned on it's side.
I seldom if ever do that. However, my wife insisted that I not march down the aisle with her as grandparents with a camera hanging around my neck. So, I gave it to a nephew and ask him to take pictures as well as movies of the procession coming in and the wedding party marching out. He did the marching out correctly, but for some reason turned the camera on its side to take it as the bride and father were coming in. I did find a program to turn it over correctly, but I'm trying to find one now that will crop the black siding out, but haven't been successful so far.