Leaf, I have Windows 7-64 bit. I bought this software a few months ago and it works terrific....
http://www.fastpictureviewer.com/Not only does it have the codec built in, but it's a great way to quickly cull images in that you can zoom it at 100% with just the click of a mouse. You can also enter keywords through the software into the EXIF (I think the shortcut is 'Ctrl-W')
edited to add - I just noticed they mention iStock inspectors use the software...that wasn't there when I bought it a few months back. Interesting.
Gannet77 - the codec for Windows XP has been out for at least 6 years. Have a look here =>
http://www.microsoft.com/download/en/details.aspx?id=8802The windows XP version does not work in Windows 7