I have a Windows10 desktop that I have been using for a long time. It is connected to my router via PLT and/or WiFi.
Around a month ago, I started noticing that the download speed had decreased, with no particular cause – to my knowledge. The Ethernet is no longer available (no internet), I double checked the wiring – everything seems fine there.

I now measure a download spee of around 2 MB/s via the WiFi on my desktop, and, at the same time, of around 150 MB/s on another laptop. Sometimes, usually after the boot, I can get a 50 MB/s download speed on the desktop.

The task monitor says there is nothing much happening on my wifi, and nothing on my ethernet port.

I don’t know how to check what is going on. I tried running an antivirus (avira), nothing was detected.

I tried resetting my network configuration (on the desktop), this didn’t change the download speed.

Is there anything you would recommend testing to find clues ?