An open-source Windows driver is available here : [FFS File System Driver for Windows](http://ffsdrv.sourceforge.net/). This driver allows you to mount a NetBSD partition using a Mount Manager (included with the driver). Currently, writing is not supported. The partition content is viewable under a windows explorer. 

_Note : Partitions are mounted the Windows way, so you have to check what are the right disk and partition numbers before mounting._