Desktop Icons for .skp files in Windows 7

When I recently began using SU, I saved a few files (.skp) directly to the desktop of Windows 7. At first, they were represented by a generic icon, but within the past couple days, the icons have changed and they are now “mini” versions of the actual project.

For example, the first project that I created was named “bench” and when I saved it to the desktop, there was a generic red-and-white icon with the file name below it (standard Windows stuff). Just recently, the icon has changed from a generic icon into a small version of the actual project…there is a small version of the bench! Same for 2 other projects that I had saved. I like this!

Has something been changed? If not, how can I make sure that whenever I save a .skp file to the desktop that Windows will represent it with an accurate mini drawing?

You installed SketchUp 2015.
All SketchUp files normally contain a thumbnail image, so there is no user action required. For being able to display the thumbnail image, Windows Explorer uses a thumbnail provider extension (from SketchUp). Windows Explorer has unfortunately been designed in a way that the thumbnail provider must be binary compatible or is otherwise not used. That means Explorer 64bit is only able to display thumbnails when using a 64bit application – like SketchUp 2015 – and not from a 32bit application.