Download DiskView, which shows you a graphical map of your disk, allowing you to determine where a file is located or, by clicking on a cluster, seeing which file occupies it. Double-click to get more information about a file to which a cluster is allocated.
The readme begins with:
Copyright (C) 2004 Bryce Cogswell
Sysinternals - www.sysinternals.com
Start Diskview.exe from its home directory. Select a volume
and press the Refresh button.