I have been using  64-bit Windows versions but there is no Canon RAW codec for it. Canon RAW codec only  supports 32-bit Windows.

I was introduced to this by FLiPMaRC at club3g.com

This allows you to view RAW thumbnails as well as opening it in 64-bit applications.

FastPictureViewer WIC RAW Codec Pack

image A free collection of 32 and 64-bit raw image decoders for Windows 7, Vista and XP.
FastPictureViewer, the fastest image viewer!     Windows Vista introduced a modern and extensible imaging framework called Windows Imaging Component (WIC). The operating system comes with built-in support for several common image formats including jpeg, bmp, png, gif, tiff and HD Photo. WIC makes it possible for 3rd parties to add first-class support for image formats to Windows, complete with thumbnails in Explorer, preview and slideshow support in Photo Gallery / Photo Viewer and metadata search integration.

The FastPictureViewer WIC RAW Codec Pack provides such platform support for additional formats through read-only image decoders, simultaneously available in both 32 and 64-bit flavor.

WIC-enabled image viewers such as Windows Live™ Photo Gallery, Windows 7′s Media Center and our own FastPictureViewer Professional “automagically” gain the ability to open and view new image formats, play slideshows etc, so does all .NET 3.x and WPF-based applications.

http://www.fastpictureviewer.com/codecs/

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