Hi AlejoOdgers,
Thanks for your purchase!
The first thing that I would do in your case is to test with a smaller video or audio, one that is one minute for example. Just drag and drop it and see how long it takes your system to transcribe it. Most probably it will take longer than that one minute since the CPU is from 2015, so it will be much slower than a more modern machine.
Now that you know how long it roughly takes (for example double the time, or ten times, whatever it is), you will be able to get a rough idea of how long it would take on your machine to transcribe that file of 1 hour 20 minutes.
Usually I would recommend using the GPU option, but for a machine that old, probably it will cause more problems than what's worth. That's one of the reason why I added this option, to be able to skip the GPU if there are any issues. So, try it without the GPU, that's the most reliable way.
Now, after you have an idea of how long it would take, run it, and leave it there doing its thing. You can check that the application is working properly by opening up the Task Manager. You will see the name of the application and the CPU usage. You can open the Task Manager in Windows by pressing Ctrl + Shift + Esc.
I would leave it overnight running, because my guess is that it would need a few hours to process a file that is 1 hour and 20 minutes. Modern machines need about the same amount as the input, so a decade old machine would need quite a bit more.