For those of us who prefer shooting NEF (raw) files: If the thumbnail images in Windows Explorer have disappeared, you can easily fix this by applying a simple Registry hack, described here:
http://www.earthboundlight.com/phototip ... p-sp2.html
The fix is done by double-cliking on a normal text file with a .reg file extension, containing the following text:
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\.nef\ShellEx\{BB2E617C-0920-11d1-9A0B-00C04FC2D6C1}]
@="{3F30C968-480A-4C6C-862D-EFC0897BB84B}"
If you have this problem on a PC running Windows XP SP2, you can also download this official Nikon NEF Thumbnail Updater (although it seems overkill to download a 592 KB file when a simple Registry fix will do, but the decision is all yours).
Jarle