The program uses a large amount of RAM, which is limited to 4GB on 32-bit systems. This could lead to instability of the operating system as a whole and would limit the maximum size of audio files.
As you know, this system is already outdated and is not considered safe. But more importantly, DirectML machine learning libraries are only available starting from Windows 8.1
All the magic happens after clicking the "Separate" button. Wait until processing is complete, and then use the two knobs to adjust the voice and music volumes separately.