To unload a hive from the registry
Open Registry Editor
Select a hive that you have previously loaded onto your system.
On the File menu, click Unload Hive.
Incorrectly editing the registry may severely damage your system. Before making changes to the registry, you should back up any valued data on your computer.
To open Registry Editor, click Start, click Run, type , and then click OK.
You must be logged on as an administrator or a member of the Administrators group in order to complete this procedure. If your computer is connected to a network, network policy settings may also prevent you from completing this procedure.
Load Hive and Unload Hive affect only the HKEY_USERS and HKEY_LOCAL_MACHINE keys and are active only when these predefined keys are selected. When you load a hive into the registry, the hive becomes a subkey of one of these keys.