Convert audio files to mp3 using ffmpeg

I need to convert audio files to mp3 using ffmpeg.

When i write the command as ffmpeg -i audio.ogg -acodec mp3 newfile.mp3, I get the error:

FFmpeg version 0.5.2, Copyright (c) 2000-2009 Fabrice Bellard, et al. configuration: libavutil 49.15. 0 / 49.15. 0 libavcodec 52.20. 1 / 52.20. 1 libavformat 52.31. 0 / 52.31. 0 libavdevice 52. 1. 0 / 52. 1. 0 built on Jun 24 2010 14:56:20, gcc: 4.4.1
Input #0, mp3, from 'ZHRE.mp3': Duration: 00:04:12.52, start: 0.000000, bitrate: 208 kb/s Stream #0.0: Audio: mp3, 44100 Hz, stereo, s16, 256 kb/s
Output #0, mp3, to 'audio.mp3': Stream #0.0: Audio: 0x0000, 44100 Hz, stereo, s16, 64 kb/s
Stream mapping: Stream #0.0 -> #0.0
Unsupported codec for output stream #0.0

I also ran this command :

 ffmpeg -formats | grep mp3

and got this in response:

FFmpeg version 0.5.2, Copyright (c) 2000-2009 Fabrice Bellard, et al. configuration: libavutil 49.15. 0 / 49.15. 0 libavcodec 52.20. 1 / 52.20. 1 libavformat 52.31. 0 / 52.31. 0 libavdevice 52. 1. 0 / 52. 1. 0 built on Jun 24 2010 14:56:20, gcc: 4.4.1 DE mp3 MPEG audio layer 3 D A mp3 MP3 (MPEG audio layer 3) D A mp3adu ADU (Application Data Unit) MP3 (MPEG audio layer 3) D A mp3on4 MP3onMP4 text2movsub remove_extra noise mov2textsub mp3decomp mp3comp mjpegadump imxdump h264_mp4toannexb dump_extra

I guess that the mp3 codec isnt installed. Am I right here ? Can anyone help me out here ?