There is a file in Windows 7 at C:\Users\[username] named NTUSER.DAT. This is a registry hive. A new hive is created for each user that logs in. The hives contain information about a user's application settings, network connections, printers, and environment settings. This is a very useful file to have when you're imaging a user's laptop or desktop. However registry files like this one cannot be copied with Windows Explorer. If you try, you'll get an error message like this one:
FTK Imager can be used to copy this files. On the toolbar, click on the yellow safe icon. A new dialog box will appear prompting the user to 'Obtain System Files'. If you select the option for 'Password recovery and all registry files', and select a folder to copy the files to, the NTUSER.DAT file will be copied with other registry files to the new destination.