Edit the registry of a WIM without having to recapture

• Mount the WIM file with ImageX:

imagex /mountrw myOS.wim 1 c:\mount 

• Load the desired registry hive (in this example it is Software):

reg load HKLM\mykey c:\mount\windows\system32\config\software 

• Open regedit and make the changes.

• Unload the registry:

reg unload HKLM\mykey 

• Commit the changes back to the WIM file:

imagex /unmount /commit c:\mount