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:

Diskview for Windows NT/2K/XP/2K3
Copyright (C) 2004 Bryce Cogswell
Sysinternals - www.sysinternals.com

Using Diskview
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Start Diskview.exe from its home directory. Select a volume
and press the Refresh button.