Press windows key+r and typ shell:startup see if theres any hidden files in there. Get kaspersky and anti malwarebytes and run a full scan.
If this doesnt detect anything thats related to the hijack such as a RAT, Trojan, you should consider backing up your files and completely clean your hard disk and start with a new operating system.
I suggest Windows 10 most stuff will be stopped by Windows Defender, but in this case I think its crypted well enough to bypass all kinds of anti virus and defenders.
If you really want to be save, try moving over to Linux and the best anti virus is YOU, dont click on stuff you dont trust, question it.
