Almost year. Are you still there? Audio CD doesn't support MP3. In fact, it doesn't have any file system, it just contains pure raw audio data and some markers for laser reader to know where to move on skip.
In order to make an Audio CD from MP3 files, you have to arrange a CUE sheet containing some info.
Open ImgBurn (install, if not already), navigate to Tools > Create CUE file...
Place your tracks there and re-arrange them as you like. You may actually include some informations about the songs and performers. Those can be inherited from the MP3 files ID3 tags. Name your mix album, set album performer to "Various Artists" and save it anywhere you like.
Technical details: Audio CD have two types of data: Raw audio data in PCM 16bit stereo format in 44.1 kHz samplerate, and program instructions for laser reader to know where to move when a skip is made (may be reffered to as time markers). Those markers are the *.cda files when you open the Audio CD in Windows Explorer. However Audio CD has no files. This is just the way Windows Explorer interprets the markers. Audio CD can contain some basic informations about the album (the songs and album credentials you filled in). Those are CD-Text data, a standard digital CD metadata format used to identify disc and every single track. CD-Text is not supported by all CD players, but a CD player without CD-Text support should essentially be able to play digitally labeled CD, it just won't show the wanted informations (it will ignore them).
Hope that shall help not only you, bur others who do not understand technical restrictions of old CD players