If someone has a Nikon SLR, he probably uses the RAW format generated by these cameras. In Windows 7 64-bit preview of NEF files is not available by default in the system browser you will not see photo thumbnails. To use this feature, you need a special Nikon NEF Codec. Thanks to the installation of the codec provided by NIkon, already on the thumbnails of the photos in the system browser, we can find out what is in the photos. Then we no longer need to use Adobe Bridge, ACDSee and similar image viewers
Below you can see how it looks in practice.
NEF files without preview
This is what RAW files look like in a Windows system browser that does not have a codec loaded.
NEF files after uploading Nef Codec
If you upload the codec, reboot the system and open your photo folders, you will finally get a preview of NEF files in your browser.
Of course, they can be smaller or larger thumbnails, as you do with other graphics files in Windows.