I used to need to transcode a lot of video clips on Windows XP/7/10. So I got FFmpeg and here is my one row solution:
forfiles /c "cmd /c ffmpeg -i @file -acodec libmp3lame -vcodec libx264 -deinterlace firstname.lastname@example.org"
You can put this in Windows comand line or make bat file out of it. After that all video files could be easily merged by FFmpeg concat.
You’d better download FFmpeg for Windows from official website, it’s free. You do not need to install FFmpeg on Windows, just unzip the file.