I came into this Computer forum looking for updates on security ware and saw your post.
I installed the Tor Browser Bundle with my Firefox broswer.
https://www.torproject.org/ . I read your post and looked for an Add-On to prevent this same issue on my computer.
Firefox "Procon Latte Content Filter" , which is a Featured Add-On in the Add-On's options at Firefox site, was the one I picked to install.
I disabled my AdBlock, which is also a Firefox Tor Browser Add-On, and could not believe the advertisements that pop just on the home page and even prior to log-in.
I enabled AdBlock and they vanished. But, and this is why I write you becuase I think I know where your pornography registry entries came from. At least in part.
When I tried to Log-on here the homepage showed up just fine and then it blinked off. The Procon Latte Add-On blocked this site because it's content violated the rules!
Procon Latte has language filter blocks, which this site doesn't permit foul language in any case. But what evidently was being blocked was something in the advertisements as well becuase Procon Latte is suppose to block pornography and all things deemed unsafe for families.
If you go the route of reinstalling your Windows OS again, or you revert your computer back to factory, I highly recommend loading the
Tor Browser Bundle when you get Firefox browser. Add
CCleaner to test your registry to make sure no porn sites sneak in in the course of your browsing. Add the AVAST antispyware free version. And absolutely get the
Procon Latte Ad-on as soon as you finish installing Firefox. Along with
"NoScript", for script blocking, and
"AdBlock".
You should be good to go.

I sure hope I am after all that. :o
Just me.
I'm thinking maybe I picked up something from Facebook?
I reinstalled Windows 7 home just to be certain because after I installed the CCleaner and ran it I checked the registry again. The porn entries were still there.
I have no clue. But I'm going slowly now with what I have installed and I'm checking the registry via the "find" option to see if "porn" pops in a search. So far so good.