No sound means probably you don't have the a52 codec installed. Get it here,
I wouldn't install ffdshow, because unless you disable video thumbnails in the system registry, opening a folder with video files in it will crash explorer.
At least that has been my experience with XP.
In practice, I have found it to be better to convert to avi, and then convert those to NSV. Audio sync problems are very common, even with the most optimal settings I could figure out when encoding from mpeg2. Plus the scaler in nsvenc is so slow it's pitiful (no mmx or sse code I think).