Boot windows into safe mode and try installing there.
I would download the utility again to make sure it is not corrupted.
Apple do not inform the community of when they will release software.. just after they release it.
It is now a couple of years since Apple updated the utility for windows and it is completely out of date for the new AC version routers so Apple appears to be in no rush to help windows users.
The iOS version airport utility I guess allows most windows users to setup their AE sufficiently that they cannot now be bothered with a port to windows.