Hi, I've got some problems. When I finish to download some mp3 files I want to burn an audio cd with this songs, and then the PC says that the mp3 file is not supported or is not installed the right mp3 codec.
Later, I download the same file again, and the same warning appears when I try to burn an audio cd.
What can I do? What happens? Thanks for help me.

Which program are you using to burn CD's? If it's wmp, then yes it tends to suffer from lack of codecs. I think for m4a files you need the 3ivx codec. Have a look here CODECs list and alternate players for Movies

I'm using 'Nero StartSmart' to burn Cd's. But mainly my problem is that the nero and the wmp can not play some mp3, but the limewire plays all the mp3, so I don't understand what happen. Thanks Bro.

Have you checked for updates from Nero's website? Which version of Nero do you have? Here's some nero links 1. http://www.nero.com/nero6/en/Support.html
_ 2. _ http://www.nero.com/nero6/en/wma-plugin.php
_ 3. _ http://www.nero.com/nero6/en/Updates_prev.html

There's only 2 types of mp3 I'm aware of. One is mp3 & the other is mp3pro. Except for a very rare type that allows for higher than 320 kbps bitrate. Other than mp3, there's ogg vorbis, m4a/mp4, & wma & rp.

It will still probably be worth getting the codecs pack. Check the audio codecs at the top left here http://www.free-codecs.com/
I'm not sure whether nero requires its own codecs or not.