Since Canon does not seem to want to support 64 bit versions of Windows, many Canon/Windows users are having to hit the net for a codec solution. I being one of them, found this nice free program @ http://www.faststone.org/FSViewerDetail.htm. The FastStone Image Viewer supports most new RAW formats.
What I was really looking for was a way to view thumbnails in Windows Explorer, which you can find here: http://www.ardfry.com/cr2-codec/. It’s $30 for CR2 support, which is pricey since it’s only CR2 support. DNG and NEF are also $30 each. If you can not live without thumbnails in Windows Explorer, it seems to work fine. I downloaded the trial version and it worked as stated. But for the price, FastStone Image Viewer can’t be beat.