Just that. I bought a CD player expecting it to play, well, CD’s. It doesn’t play just any CD though, but why not?
I’m confused (and maybe you are too). What did you buy: a DVD player or a CD player? And what did you expect it to do that it isn’t doing?
Do you mean that your CD or DVD player won’t play CDs containing MP3 files, rather than actual audio CDs? If so, that’s because it’s a whole different file type.
a stand alone DVD player can likely play most all mp3 files.
some stand alone CD players, as an added feature in more expensive models, can play audio discs with mp3 files.
not all audio files are mp3. audio CDs are a different format.
more information is needed to know what you are asking.
Johnpost, “Audio CDs are a different format” covers my question, I think.
I buy MP3’s online to listen to old time radio shows, all in the MP3 format.
Why the heck doesn’t a CD player play everything?
More money for the sellers, I guess…
listening to OTR mp3s is a good time.
look in the specifications for a CD player if it plays mp3 or Yellow Book standard (then it will play the mp3 files). years ago i got one for $60 when ordinary CD players were about $40.
you can put mp3 files on a CD data disc and play it in a computer or stand alone DVD player.
you can use a small mp3 player, i have a couple different Sansa models. store the data on your computer HD or a CD data disc or a DVD data disc and load up into your player. listen on headphones or through some amplified computer speakers. these players can be had for $2 to $30 on the low end.
Some CD players can play other file types, but most are designed to play just the CD’s you’d buy at a record store (do they still have those?) 
You’ll have to look at the technical specs of the CD player to see what it can play. For example, this Sony CD player will play MP3’s burned to CD.
Here and here are a couple of older threads that include explanations of the difference between audio CDs and MP3s.
MP3’s take software to decode. It’s a lot more complicated than plaing the “wave” format files that are on audio CDs.
Audio CDs have a very simple layout (well, compared to a computer filesystem … sorta … but let’s ignore data recovery etc.) It takes more CPU horsepower to handle a computer filesystem (which is what you need to store MP3’s) and decode the MP3’s and turn it into raw audio data (which is pretty much what “wave” format data is).
However, you CAN convert your MP3’s and burn them onto a normal audio CD, using just about any CD-burning software. All you need is the right app to mix your own CDs from the MP3’s you’ve downloaded.
The disadvantage to burning an audio CD (versus MP3 data format CD) is that with the former, you’re limited to 80 minutes of audio; with the latter you can have hours of it (depending on what MP3 bitrate you use). The advantage to audio format is that it’ll play on any player.
Well, except some that came out before burnable CDs and can’t read CD-Rs.
That’s another possible problem, BTW. Even if your CD player says it can play MP3s, if it does not mention CD-RW compatibility, you may be forced to use non-rewritable disks (CD-Rs).
Jeez! Can it get anymore complicated? 
also if your player is capable of playing mp3 data files you should make note of the parameters that it can handle. then only get mp3 or encode your own with those parameters if you plan to play them on that player. usually not a problem because most good quality audio parameters are OK.
also CD+R discs are preferred by many over the CD-R discs.
I appreciate your effort to make it more complicated for Jake, but what’s a “CD+R” disc? Were you thinking about the distinction between “DVD+R” and “DVD-R”?
yes DVD. what a total brain fail on my part. i’m multitasking and popping in here making a reply without my brain being fully engaged.
I feel your pain. But consider the development (or evolution) of the 5" disk player, from stamped CDs to burnable CDs, stamped DVDs, burnable DVDs, and then consider the formats: CD music, CD computer data, DVDs… Each one has a different kind of index (directory) and file parameters.
And I’m leaving out the -R, +R, RW, CDRAM, etc. which is also a factor.
It’s amazing that the underlying data structure is pretty much same as it was in the 1980’s (cross-interleaved Reed-Solomon code, Huffman encoding, block storage, etc.)
I have a BSR music CD player from 1989. It works perfectly for what it was designed for, but MP3s didn’t exist then, and computer data storage was uncommon, so how would you expect the manufacturers to handle future formats?
The good news is the latest hardware seems to be able to handle most of the formats likely to be thrown at it.
Jake, here’s an attempt to answer your “Why” question (though it may just be a rehash of some of the things said earlier, in this thread and in the other threads I linked to, as well as Musicat’s latest post, which wasn’t there when I started writing this):
If you got an older CD player, there’s a very simple reason why it wouldn’t play MP3’s: MP3’s weren’t invented yet. Audio CDs were all there were, and CD players played them just as record players played (vinyl) records and cassette players played cassettes.
Then, someone developed a way of storing computer information (software, text files, pictures, etc.) on the same style of disc. Discs that contained this sort of computer information were originally mainly mass-produced and store-bought, and were called CD-ROMs. (The “ROM” stands for “read-only memory.” Your computer would only be able to read what was on such a disc and, assuming it had the right kind of software, to decode/play/display/run it. Your computer couldn’t store anything new on the disc.) Then, computers started being sold with CD burners, which allowed you to create (“burn”) your own CDs, called "CD-R"s or "CD-RW"s depending on whether they could only be written to once, or whether they could be erased and rewritten.
People also developed ways of taking the digital information that described music/sounds, and compressing it so that it can be stored in a computer’s memory, hard drive, etc. in a relatively small amount of space. The MP3 format is one of those ways (probably the most common/popular). Your computer plays MP3s with the help of software that decodes the sonic information included in the MP3 file. So, MP3s were one of the many kinds of computer information that could be stored on a CD-ROM or CD-R or CD-RW.
Anything that can be stored in your computer can be stored on a CD-ROM or CD-R or CD-RW, assuming it doesn’t take up too much space: documents, pictures, programs, MP3s, etc. But of course, you can’t expect a CD player to “play everything”—what would it do with a photo file, or a video file, or a spreadsheet file? It could do something with MP3 file, but only if it knew how to decode the MP3 into sound. This is certainly possible, but requires special software (and maybe, more sophisticated user controls). As time went on, more and more CD players were being manufactured with this capability built into them, but that makes them more expensive.
I haven’t even mentioned DVDs (or Blu-Ray discs), which have the same size and shape but which require a different kind of laser to be able to read (and which can store a lot more information). Most (but not all) DVD players (and as far as I know, all computer DVD drives) can also read and decode CDs (as a kind of “bonus” ability), but not the other way around.