If anyone is interested there is a package of free windows codecs for most raw formats, including some MFD, Hasselblad, Leica and Mamiya - af http://www.fastpictureviewer.com/codecs/
DNG is supported as well. What is really great, is that I use these codecs on Win7 x64, as they are native 32 and 64 bit.
The Fastpictureviewer itself is a wonderfull application. It is supporting GPU acceleration and XMP for quick file rating.
I use it for tethering Nikon, though it supports many other cameras as well.
Support from the developer is great, I just recently requested codec for Mamiya MEF files - and voila! I can see their thumbnails in windows explorer.
Just spreading the word in gratitude:)