A hidden file is any file with the hidden attribute
turned on. Most Windows powered computers are configured by default to not display hidden files.
Configuring Windows to either show, or hide, hidden files is relatively easy:
The pagefile.sys file is a common hidden file in Windows. ProgramData is a hidden folder you may see when viewing hidden items.
In older versions of Windows, commonly encountered hidden files include msdos.sys, io.sys and boot.ini.
Examples: "I created a boot disk for Windows XP but did not find the necessary files on it when I looked at the contents of the disk. I finally realized that the essential boot files were hidden and not normally viewable."