With drive letters, a neat functionality in DOS/Windows command prompts (don't ask me about Powershell) is that each letter can have its own "current directory".
So if you have ffmpeg.exe in C:\Program Files\FFMpeg\bin, and you have some source files in D:\SourceVideos, and you want to process them in ffmpeg and output them to E:\Output you can do:
C: (to navigate to the C: drive)
cd "C:\Program Files\FFMpeg\bin"
E: (to navigate to the E:\ drive)
cd D:\SourceVideos (you remain in E:\, but the "current directory" for D: has been changed).
cd Output (to enter E:\Output)
You can now do C:ffmpeg.exe -i D:scene1.mp4 output-scene1.mp4
and Windows accesses the files in the "current" directory on each drive letter.
So if you have ffmpeg.exe in C:\Program Files\FFMpeg\bin, and you have some source files in D:\SourceVideos, and you want to process them in ffmpeg and output them to E:\Output you can do:
C: (to navigate to the C: drive)
cd "C:\Program Files\FFMpeg\bin"
E: (to navigate to the E:\ drive)
cd D:\SourceVideos (you remain in E:\, but the "current directory" for D: has been changed).
cd Output (to enter E:\Output)
You can now do C:ffmpeg.exe -i D:scene1.mp4 output-scene1.mp4
and Windows accesses the files in the "current" directory on each drive letter.