That's called ripping, to get music (or spoken text in case of books) from the CD to mp3-format. Windows Media Player does it. And you can find other programs that do it also, like CDEX (free).
A CD is 700 MB. A music mp3 is about 1 MB per minute. For spoken books you can lower the quality (if your ripping program allows it) so it's only 0,5 MB per minute.
1 MB a minute = 8000 minutes in 8 GB = 133 hours to listen to in 8 GB. That's enough?
Kees
I want to burn books on CDs to my computer & then download onto an MP3 player (which I have yet to buy). Also,tips on the best was to this would be greatly appreciated! When purchasing an MP3 player, should I just get an 8GB just to be safe? How do I determine how big the entire book on CD file is? Lastly, are there any avid listeners of books on CDs who can recommended decent audio book sites? Thank you very much!

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