PPRuNe was, by accident, infected with advertising popups some time ago - You could do a search, but at the time I installed
Panicware popup stopper at the time and it has been available on my machine ever since. It does interfere with some of the win 95 help systems and stops you playing solitare though. A couple of quick clicks on its icon on the bottom rhs of the screen (a right one and a left one) soon gets rid of it though when you want to play cards!