Latch

You don't want to convert from WMA to MP3 (or vice versa) unless you really need to. That is converting from one lossy (as in, when the file is orginally encoded, some parts of the song didn't get encoded and were left out to help compression) format to another lossy format, so basically you're degrading the quality of the song twice. Doing it once (from WAV to MP3 or whatever) is not too noticible (except for Audiophiles), but do it twice and you'll notice it. Your best bet is what they said above, or get the original CD and rip it to the format you want, or look for the files in a lossless (no data left out) format (SHN is an example format). If you converted to SHN to WAV, and then to MP3, you'd end up with a file that sounds like you ripped it from the original CD.

Some of this stuff doesn't apply to you (If you converted a SHN to WAV, you'd have no need to convert it to MP3 for your CD), but thought I'd say it anyways.