Windows Vista does not generate thumbnail image for .NEF (Nikon RAW image) files. Also, Windows Photo Gallery cannot open .NEF files by default. Here is a tip that tells you how to add thumbnail and Preview support for .NEF files in Windows Vista.
Nikon RAW Codec is a software module that enables you to handle RAW image files (*.NEF: Nikon Electronic Format) under Microsoft® Windows XP SP2 and Microsoft® Windows Vista® with the same ease as JPEG or TIFF images. After installing the Nikon RAW Codec, Windows Vista will be able to view thumbnail preview for .NEF file types in Windows Explorer. Also, Windows Photo Gallery will be set as the default handler for .NEF file types.
Download Nikon RAW Codec (27.4MB) from Nikon’s Website. This applies to Windows XP Service Pack 2 (32-bit) & Windows Vista (32-bit) systems only.