Switching internal WiFi receiver to a USB dongle?

[#1]

Does anyone know how to temporarily disable a Medion i5 Desktop PC’s internal WiFi receiver in Windows 10 and try a USB WiFi dongle to see if the internal WiFi is faulty?

The reason why is in the attached document.

Please try to help - submitting this post took over 35 minutes!!!

[#2]

How do you know that it's a wireless problem? Have you tried connecting the router to the computer using an Ethernet cable? 

What router are you using? What is the distance between the router and computer and are there walls in between?

[#3]

Plusnet sent me a new router - same problem.

I've tried an ethernet cable, ,but because of the house layout I had to use 2 x 20m phone cables to get the router near enogh the PC. In fact, the router is one floor down and about 2 metres away - worst case it's 5 metres from the PC with no intervening brick walls.

I now suspect the PC's built-in wifi receiver (my Kindle Fire works fine using the new router), which is why (as I happen to have a wifi dongle from my old PC) I am trying to disable the on-borad wifi device and enable the dongle, to see if that works.