If you create a standard audio CD, you can fit 80 minutes worth - this usually equates to 15-20 songs, assuming each song is 4-5 minutes long.
As already mentioned by accordion, you'll get many more on in MP3 format, as this is governed by the files' sizes (which is in turn determined by a song's length & file bit-rate/quality).
So with an average file size of 4-5Mb, you could easily fit 150-175 MP3/WMA/other file format songs on a single 700Mb CD. But first you'll want to determine if your player can actually play MP3/WMA/other file format CDs! G