Other Why do I get the device connected/disconnected noise when the downstairs light is turned off?

The kitchen light.

And when I turn off the (regular) fan when it's plugged into the same extension as the computer.

 

Ok it's the kitchen light doing it for whatever reason.

 

That's a weird one, is your power supply a fancy one that has a USB connection direct to the mobo for monitoring? Does it do it if your pic is plugged into the wall rather than an extension?

 

Just a regular one that's plugged into the socket in the wall.

And this hasn't happened for weeks since, but at some point it'll happen again for no forseeable reason.

 

What device is connecting and reconnecting?

 

Are you using homeplugs/powerline adapters?

 

Nothing? Don't know.

Don't know the brand, if it has one.

 

I've had an HDMI connection that disconnects and reconnects briefly when you turned on desk fan that was plugged into the same extension lead.

I would guess it's some sort of electrical surge/noise/interference that is being generated by the appliance when it is being turned on/off and it is affecting the PC/device because they are connected to the same extension.

 

It should be recorded in the Windows system event log, it may not help to know what devices it is but at least it will help narrow it down a little.

 

I looked that up, and I'm guessing I'm wanting to look at Hardware Events, and the answer is 0 events.

 

So that's a yes?

Maybe as simple as, the power is briefly making the network disconnect.

Try and speed test.
The another one with someone flicking the kitchen light on and off. See if there is a difference.

 

It's an I don't know, it's just a regular blank ol' extension plug.

My network speed? I'm having no internet problems.

 

When he said homeplugs/powerline adapters, he meant network plugs through the electrical wiring, not your extension cord.

It could well be a wiring issue in the house, at work our CCTV monitor goes off whenever someone walks through the back room (triggering automatic lights).

 

Leave a ping open to Google DNS, eg "ping 8.8.8.8 -t"

Turn the kitchen light off, do you see any pings drop?

 

Pardon?

 

Ignore, if you're not having any issues with your internet.

Do a physical check power cables, are they suitably sheilded and not damaged, how is your cable management? are power cables away from data cables? have a look at an anti-surge gangway socket.