I realize I am coming in a bit late, but there is a free RAW viewer which extends Gimp's ability to load that format. Check out UFRaw:
http://ufraw.sourceforge.net/
I'm on a Mac so it's native for me. But if you go to the install page on the website there are Windows options about half way down.
http://ufraw.sourceforge.net/
I'm on a Mac so it's native for me. But if you go to the install page on the website there are Windows options about half way down.