Hi
Have you run Malwarebytes to see if it finds anything?
This does sound like malware to me.
You should be able to run Malwarebytes from a flashdrive created on another computer, in safe mode.
If that can't be done then I'd say that Neemobeer is right and you'll have to reinstall.
Since you can't do it from within Windows, look at the Using the media creation tool option, using a DVD or USB.
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If you need to get data off of the computer first, you can make a Ubuntu disk, boot from that and copy your stuff to another drive of DVDs.
Mike