Appreciate you taking the time to put something like this together. Few observations with Opera 9.5b16702 using v1.2:
INI contents were replaced with the plug-ins section only. Remainder of contents removed.
New entry, remainder still present ... all good.
Existing MIME types were removed and replaced with:
In your next version, you may want to add logic to read the current INI values and append the changes to them if they aren't already present to intended INI sections only - ex: not [Windows Media Player] in AXOBJECTS.INI.
Lastly, would it be possible for you to provide a list of changes that occur to files, registry, etc. It would be helpful in verifying that all is as should be.