Thumbnails for Minolta Description:

Thumbnails for Minolta is a small utility that allows you to view thumbnails of Minolta raw files in Windows Explorer. The software does not convert raw files, nor does it change them in any way.

Once you have installed Thumbnails for Minolta, then thumbnails of .mrw raw files will be shown in the thumbnail view of Windows Explorer (Windows Explorer>View>Thumbnails). You do not need to process the .mrw files first.