Use CDex (Open Source, Freeware):
http://cdexos.sourceforge.net/CDex uses LAME as its MP3 encoding engine.
About Lame (from Wikipedia):
LAME is an MPEG-1 audio layer 3 (MP3) encoder. The name LAME is a recursive acronym for LAME Ain't an MP3 Encoder, reflecting LAME's early history when it was not yet a complete encoder in itself.
As of 2004, consensus amongst the audiophile community is that LAME produces the highest-quality MP3 files for bitrates greater or equal to 128 kbit/s when using VBR; in a public listening test early in 2004, LAME MP3 files were the best 128 kbit/s MP3 files compared to the uncompressed original audio when using VBR mode.[1]
Released under the GNU Lesser General Public License (LGPL), LAME is free software.
Source:
http://en.wikipedia.org/wiki/LAMEAbout CDex:
http://en.wikipedia.org/wiki/CdexA guide to using CDex
http://www.users.on.net/~alexanderino/cdex/