media on playbook not recognized by desktop mgr after switching from windows to mac

my playbook was originally sync-ed with an windows pc which died a couple months back. I have since bought a mac and have plugged the playbook into the mac and set up device mgr & desktop mgr. With that I have transferred files to & from the documents folder on the playbook.

What I have not yet done is re-sync my music, pictures & videos. What I just noticed is that according to the desktop mgr on the mac, there is zero GB of media on the playbook even though what I had on the playbook remains there and I am able to see all the media I sync-ed onto the device before from the device itself.

So before I click the sync button on the desktop mgr, is there anything I should do? What should I expect to happen when I click that button right now? Or should I back up whatever I need to back up first and then wipe that "old" media off and do a new sync as if from scratch?

As I started choosing music playlists to sync via the mac desktop mgr, the desktop mgr seems to show the selected media will be added on top of what was already there. I'm wondering if I should just delete all those pre-existing media files before I sync.

Thanks.

BACK UP NOW!!!!

I am someone who does not trust any sync. It could decide that the "empty" media is the way you want it and automatically DELETE the matching (non-matching) stuff on the computer. Or it could double every file (not as bad).

I manually move/copy my various media files manually using drop and drag. That way no computer decides which device (pb or computer) is the master. I may be a bit more work but at least I will not watch frantically as files start deleting that I want.

After a backup, you can then make sure syncing works as you intended.