http://en.wikipedia.org/wiki/Compact_Disc_Audio_track
A CD Audio Track or .cda file is a small (44 bytes) file generated
by Microsoft Windows for each track on an audio CD. The file
contains indexing information that programs can use to play or rip
the disc. The files are given names in the format
Track??.cda.
The .cda files do not contain the actual PCM wave data, but instead
tell where on the disc the track starts and stops. If the file is
copied from the CD-ROM to the computer, it becomes useless, since
it is only a shortcut to part of the disc. However, some audio
editing and CD creation programs will, from the user's perspective,
load .cda files as though they are actual audio data
files.
i think you need to rip the cd to make the songs playable on PC
...
