Macromedia - Optimize Your Library Items In Flash
Here's a quick way to trim your Flash file of unused Library items. Open the Library (Window > Library) and access its dropdown option menu. Choose Select Unused Items to highlight the offenders and then delete them by pressing [Delete]. If you want to view how many times your active Library items are used, open the menu again and select Update Use Counts now. This can be very useful when trying to optimize your file to see areas where you can combine Library items to produce a more streamlined Flash movie.