Windows update KB2862330
Please don't groan if advice on this botch is posted here somewhere. I've searched and I can't find it.
I've also tried uninstalling it, as recommended on the Microsoft forum, but back it comes, causing my wife's laptop - Windows XP Home Edition Version 2002 Service Pack 3 - to do the double boot-up thing.
So far, it isn't doing anything worse, unlike some people I see on the search engine.