How to remove the MSN pop up permanently?

That one you're pointing to refers to Firefox, and Skype. Not sure what that's all about, but you could disable that one as well.
Then let's see the Windows tab, and the Internet Explorer tab please.

DeaconFrost said:

I don't see anything crucial in that list that couldn't be turned off. I don't see an AV entry though.

I don't see how turning off the Flash updater is a good thing?! Honestly, it just leaves the system vulnerable.

Arcadian said:

Lost me a bit now with "Windows tab" ? And I don't use IE Explorer only Firefox... ?

Yes, I realize you don't use Internet Explorer, but THAT is what is opening on you.

Everything that I can see in the IE tab looks okay. Can you scroll down in the Windows tab so I can see the rest of them please?
What email/method/client are you using for POP Peeper?
I will be afk for about half an hour.

I agree with Deacon Frost - there's nothing in startup that can't be disabled.
cCleaner SkipUAC is nice to have so you don't have to answer the UAC dialog box

Flash is different on Win8 / Win10.

Flash Plugin - Keep it up to date and troubleshoot problems | Firefox Help

Installing or updating Flash
The Flash plugin automatically updates itself by default. If Mozilla's Plugin Check page or Adobe's test page says that Flash is outdated and you don't want to wait for the automatic update, you can update Flash manually by downloading and installing the latest version from Adobe.

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Getting back to the issue, please check the following settings:

What browser is set as the default browser?
--> Make sure set defaults shows Firefox

What is the home page for that browser?
--> Test: configure browser to use blank page or new tab

Arcadian said:

I use GMail....thanks

Okay. Did you have a look where @essenbe mentioned?

Task manager in search > Open Task Manager > Go to startup tab.

Looking for Internet Explorer, or anything MSN or Bing?