After installing this week's Windows Updates, I notice that the GIF and JPG icons on my computer have changed ... and when I try to go into "Folder Options" and change them back, the change doesn't take.
This smells like a VBA problem. VBA (Visual Basic for Applications) is the language used for automating MS-Office. MS provides an object model API for every office application that's pretty well documented. (example - http://msdn.microsoft.