When you sync, you are not sync'ing up against anything. Just the little creatiion you are making in emplode. Sync'ing does not mirror a database of tunes on your pc. If I had the space (and now may look into getting a 3.5" HD USB case with a monster drive) that would be neat though and several people have brought it up.

I have about 600+ CD's.

The hard part: Not only were all my Cure CD's removed (a simple week's worth or re-ripping) but so were their songs from any soundtracks or compilations. Also, any Cure covers by other bands. I kept all of these in the "Cure, The" playlist in "Artists A-C".... Not too mention any of the rare stuff that is out of print like The Cure's "Purple Haze". The same goes for the Chemical Brothers which contained all of the tons and tons of remix work they had done.... Crystal Meathod, The Church, The Cult, Charlatins UK. etc etc