Just because your MP3 player doesn't support AAC -- the format used by Apple's iTunes Store -- doesn't mean you can't still play those files. It's simply a case of converting the files from AAC to MP3, and that's something iTunes will even do for you. We're going to show you how.
Important warning first
AAC is a compressed music format, meaning bits of audio data have been sacrificed in order to get a CD audio file into a manageable size for an MP3 player. To most people, the results of this compression aren't even audible. But converting from 'lossy' AAC to MP3 (another lossy format) means a little more data vanishes into the ether. It's only small, but it's worth bearing in mind.
We're going to advise that you encode in the highest possible MP3 bit rate (320Kbps) in order to minimise this loss of audio fidelity.
First things first
Ensure you download the version of songs from the iTunes Store. These are DRM-free and can be easily identified by a little plus symbol next to the 'Buy Song' button. Consult this guide for detailed instructions on how to ensure you're getting iTunes Plus versions of songs.
All ready? Let's get going with step one...