File Menu: There is a standard menu at the top left of the Registry Editor window with File, Edit, View, Favorites, and Help options. The File Menu contains the Import and Export controls and you can use these to back up and restore individual keys, settings for whole applications or devices, or the entire Registry.
Backups of the Registry are saved with the registration file (.reg) extension, which are plain text and can be opened with Notepad, as shown in Figure 2-3. This means that it is always advisable to store your .reg backup files in a secure and encrypted location, as any plain-text file in the workplace that might be susceptible to theft by an individual or through the use of malware might reveal sensitive data, such as domain information, that you would not wish revealed.
Typically a .reg file will contain Registry information exported from one Registry. If this .reg file is then run on another system, the information contained in the .reg file will be imported directly into the Registry.
Also in the File menu are options to load and unload a Hive. This is a file that contains a portion of the Registry but that may be currently inactive, such as being applicable for a different user on the machine or not being applicable to the current Windows session (e.g., if you’ve booted from a Windows install disc and are editing the Registry from that).
Load and Unload Hive will permit you to manage these additional Registry files for viewing and editing. By default in Windows these options are grayed out and unavailable until you select HKEY_LOCAL_MACHINE (or) HKEY_USERS.