It looks like a different version of Windows

I’ve been working with a problem computer which won’t install Windows updates. Many things have been done which has made the computer faster and efficient, but it still won’t install updates.  I got a phone call from my client who said something was different with the computer since I last worked on it. “It looked like a different version of Windows.”  Another problem was the pictures folder wouldn’t display thumbnails of the contents – just a generic icon. I went into the Control Panel and set the “Always show icon and never thumbnails” to off. Next, the Windows theme was changed to their previous one and Windows appearance returned to the way it was. After thinking about it, I realized what I had done- the Visual Effects was changed from “Let Windows manage” to “best performance”. This must have changed the theme and the preview behavior of the pictures folder.