How to merge Windows registry hives directly without converting them to an intermediate text based file?

Help! I'm going to get fired if I can't figure out how to do this by tomorrow.

Microsoft Windows stores its registry databases (known as "registry hives" there's actually a backstory to the origin of this name, but I digress) in a proprietary binary format.

Answer this correctly or you lose your job:

1. 
   

   Let H-sub-A be the registry hive of Computer A, and let H-sub-B be the registry hive of Computer B.

   
   


2. 
   

   Create a registry hive H-sub-A-prime (in the native binary format) that contains all of the registry keys and values in both H-sub-A and H-sub-B. If there is overlap, let the value from H-sub-B overwrite the value in H-sub-A.

   
   


3. 
   

   Sure, you can import a text-based patch file (e.g., "FOO.REG") to modify the registry, but can you merge two registry hives in their native binary format?

   
   

Answers that involve exporting the registry to a text file (e.g., "FOO.REG") will receive no credit. You may only use software included with Microsoft Windows (any version) and / or third-party tools that are free of charge.