Do you have lots of music files in lossless or good quality formats such as flac or ogg? Do you also have an mp3 player that just won't play your good formats? Music2MP3 batch converts files from anything to mp3 and maintains the original file structure! And you can use regular expressions to select just the files you need.
This application requires the .NET Framework to be installed, which is available via Windows Updates or here: https://www.microsoft.com/en-us/download/details.aspx?id=48130
Nice reminds me of this one sourceforge.net/projects/guerillaconvert/