does anybody know how to get the 8100 to play song purchased from the itunes store? the media player in my blackberry won't play songs bought from itunes but will play other mp3 files.

Music from the iTunes store is in the AAC format, not MP3.

All songs (for now) from the iTunes store are DRM locked. You cannot play those files on an unauthroized device. Right now only iTunes and iPods and the very rare Motorola iTunes phones can play AAC files in the M4P format.

iTunes and other DRM AAC files have the M4P file extension. Native AAC (no DRM) has the M4A file extension.

If you do a little searching, and depending on your iTunes version, you can strip the DRM from your iTunes purchased music. Look for JHymn. JHmyn, last I checked will not work with purchases made on iTunes 7 and above.

Once Apple gets everyone on board with removing DRM from iTunes you will probably see a very similar tool made available.

Follow the instructions on this website and you should be okay.
bpurcell.org - Converting Itunes protected files m4p to mp3 files

Google is your friend.