In Windows Explorer :

Click Organize / Fold and Search options / View [tab] / Files and Folders section / untick "Always show icons, never thumbnails"

Seriously - what ****-head, numb-nut set this as default ??????

Oh and you need to close and restart Explorer to see the effect.
 
That's like washing your car and having to get into & out of it before you see the clean car. (:
 
 
 
(from a friend, reproduced with permission)