To add to what manx said: OpenMPT does
not blindly remember a list of audio device that are or were present on your system, in particular not between application restarts. The entries in mptrack.ini are just the settings that OpenMPT would apply if you switched back to that device, but they will stay in mptrack.ini regardless of the device driver being present or not. Hence, as long as a device is presented in the options dialog, it means that it is still registered in the system in some way or another. In particular, any other application that can handle that specific kind of audio driver (ASIO) will also see this device.
According to the website manx cited:
Use the provided uninstaller to install JACK from your machine. Note that because the 64-bit JackRouter had to be manually registered as described before, you’ll have to unregister it as well. Use the following command to unregister the 64-bit JackRouter:
regsvr32 /u "C:\Program Files (x86)\Jack v1.9.8\64bits\JackRouter.dll"
If you executed that command,
it will only uninstall the 64-bit version of JackRouter. That is exactly what is written there. I can only guess but replacing "64bits" by "32bits" in the file path will probably unregister the 32-bit version as well.
