You're smarter than you think--you got yourself a Mac. MP3s have to be "extracted" to play on CD. Check your burning software to see how best to do this. Or go to versiontracker.com and pick up a shareware program for extraction, such as MPeggerDrop Decoder, then burn your new .aif files. If you have an MP3 player, you don't need to extract. (Keep in mind that your compressed MP3s will become uncompressed audio files once extracted and then take up much more disc space. Once burned, store the MP3s to play in iTunes and just trash the cumbersome .aif files.) Have fun.