Need to get rid of pop-up screens

I would recommend Malwarebytes to git rid of your current issues.

Then you're going to want antivirus to stick around beyond that. Norton is included with my Internet service, so I've stuck with it (it's not nearly the system resource hog it used to be). The last free antivirus I used was AVG, and it worked fine for me. Looks like PC Magazine still rates them highly.

But PC Magazine includes Malwarebytes in that list, and even Malwarebytes says it's not antivirus. Avira also gets pretty good reviews.

Get a known safe thumbdrive. Download Adaware and Malwarebytes to the thumbdrive. Run first one then the other.

Generally speaking, I'd run Malwarebytes twice then run Adaware twice.

Don't install them; run them from the thumbdrive.