Thanks to everyone for their advice.
I actually went to Micro Center (where I bought the PC) first thing on opening Saturday and got a very competent and friendly technician who cleaned it for me. He ran a second scanner as suggested above, something that does not run in real time which he therefore did not recommend for home use. I then sat there for an hour while a scan was done. Cost me nothing since they never checked it in for diagnostic.
I scanned at home again which found one more infected file, but ran it again a few times and nothing more came up. Those funny websites are gone, and 'defender' does not come up with anything more.
So I think I'm OK, knock on wood.
I will definitely look into malwarebytes.
As for Mac vs. PC, I asked around and apparently Macs are starting to get viruses as well. However, they are much less frequent, so there is a good chance my next computer will be a Mac. This one is still quite new...
Bertrand.