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 -

Using Diskview

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