Microsoft RAW Image Thumbnailer and Viewer for Windows XP ..unless, of course, you're running Vista (but why would you?)
about:
Version 1.0 build 50 now supports the Canon EOS 5D and Nikon D50, D70s and D2001 cameras.
RAW image capture is preferred by many serious-minded photographers to preserve all the subtle color and detail possible from digital cameras. However, until now it has been impossible to view thumbnails and previews for RAW images in Windows without use of special software.
The Microsoft RAW Image Thumbnailer and Viewer enhances the Windows XP photos experience by providing thumbnails, previews, printing, and metadata display for RAW images from most Canon and Nikon digital cameras. This tool enables advanced digital photographers to organize and work with RAW files directly in Windows Explorer in much the same way as with JPEG images. No more guessing which image is which!
Version 1.0 build 50 of the RAW Image Thumbnailer and Viewer supports most models of Canon and Nikon cameras capable of RAW capture, including the latest professional models such as the Canon EOS 5D and Nikon D2x. (A complete list of supported cameras is provided in the readme file and in the related white paper.)
It also includes fixes for a number of known issues in the original release of the software, including the TIFF file locking issue. In addition, there is a new Save As button.
NOTE: it requires 'doze validation (but we're all good, above board legal users here, ain't we?)