A user is renaming a .

This issue happens when Windows is hiding known file extensions. If extensions are hidden, the user may only be changing the visible name (for example, changing “Document” to “Document.xml”), while the real filename remains something like Document.xml.txt. Windows Explorer then displays “Document.xml,” but file properties still show the true type as Text Document (.txt) because the actual extension at the end is still .txt, and Windows determines file type by that extension. The fix is to show file extensions by turning off the “hide extensions” behavior—i.e., uncheck “Hide extensions for known file types” in File Explorer Options/View settings. Quentin Docter specifically calls out that “Hide Extensions For Known File Types” is commonly changed because seeing extensions is “really handy,” and shows steps to deselect “Hide File Extensions For Known File Types.” The All-in-One guide and Mike Meyers’ Lab Manual both reinforce that you toggle extensions by deselecting “Hide extensions for known file types.”