Although the registry (referred to as registry hives) appears to be in one file, it is actually placed in several files on your computer.
Depending on your system configuration, registry files can be found in the following locations:
The HKEY_CLASSES_ROOT, HKEY_CURRENT_CONFIG and HKEY_LOCAL_MACHINE hives are stored in the Default, SAM, Security, Software, System files in C:\Windows\System32\Config\.
The HKEY_CURRENT_USER hive is stored in the NTUSER.DAT in that user's profile folder usually C:\Users\username.
To load a particular hive from a second hard disk connected to your system, follow these instructions.
1 Click the "Start" button and type "regedit" into the Search field, then click the "Registry Editor" program.
2 Click "HKEY_LOCAL_MACHINE" in the left pane of the Registry Editor window.
3 Click the "File" menu and choose "Load Hive."
4 Browse to the secondary hard drive's "windows\system32\config" directory from the "Load Hive" dialog box.
5 Click to select the "System" or "Software" file (no file suffixes) to open the respective registry hives. Type a temporary name and click "Open" to open the hive.
6 Once the registry hive is loaded into the registry editor, traverse down to the below path
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\ComputerName\ActiveComputerName
Here you will find the Computer name for the second hard disk.
Important: Once you have done with browsing the registry, Click the "File" menu and choose "Unload Hive" before closing the registry editor.