Go to ;
"Control Panel" --> "Folder Options" --> "View"
Choose the options you need and close the menu.
In Explorer go to "View"
Choose "Extra Large Icons".
You should now see the images you want to see in image folders;
If there are some images you still can't see, then you may need an add-on in order to display them.
This is good; http://www.uvviewsoft.com/
as is this; http://graphicssoft.about.com/cs/ima.../gr/xnview.htm
You can also get other add-ons to display various image formats in Explorer; http://www.alternatiff.com/
( This is really excellent!).
or dedicated image viewers; http://www.faststone.org/FSViewerDetail.htm