Hi HDz,
Good day! This is Jhakesong an Independent Advisor and I will be happy to assist you with this.
You mentioned that you want to re assign the headphones key to a different program in Windows.
I am not sure what is the model of your keyboard at this point. But generally if that keyboard is compatible with the Microsoft Mouse and Keyboard Center you should be able to remap its keys.
Here's how:
https://support.microsoft.com/en-us/topic/how-d....
Hope this helps. Have a great day!