Hi Rhee,
The easiest way is to add a CAML query Content & Structure reports (Site Actions -> Site Settings -> View All Site Content -> Libraries -> Content & Structure Reports)
<Where><Geq><FieldRef Name="CheckoutUser" LookupId="TRUE"/><Value Type="int">0</Value></Geq></Where>
Access the same from Site Actions -> Site Settings -> Manage Content & Structure -> Change the view to the one which you have created in the above step to get all Checked out Files.
Cheers,
Maruthu
Please click the 'Mark as Answer' if this post solves your problem or "Vote As Helpful" if it was useful! :)
