I started to run the Media Usage Report with the following items checked on the right:
Individuals to include immediate family
Items to include: show divider between media items
Filter media by: Show unlinked media
It is now 10 hours later (I was gone all day) and the report has still not appeared.
running version 21.0.0723 on a win7 SP1
with 8GB Ram and and a core 2 Duo chip.