Well its not often I go as far as to say 'Must Have' but this deserves it.
Its a codec plug-in pack that handles well pretty much everything in full 64bit glory. So this means that windows explorer at al will be able to display your RAW images, quickly, these are very well written.
for $10USD its a bit of a no briner imnsho.
http://www.fastpictureviewer.com/codecs/