I finally solved it!
It was the command-line tool (or child process) that didn't work as expected in Windows.
Like I said earlier, the program worked fine when running it directly in the DOS prompt, but for some reason didn't generate any output (in Windows only) when running it from the main application using TProcess(Ex).
The changes I made to the command-line tool was:
1) I added a missing
2) I replaced "Crt" with "Classes". (no clue what I used "Crt" for in the past)
I have no clue how this fixed the output, but now it works.
In Windows, I don't get any lines cut off after 80 characters, so I assume that's a Linux thing.