MCreator issue tracker has been migrated to GitHub.
Existing tickets have been migrated to GitHub. Please open new tickets on the GitHub tracker instead. If you do not have a GitHub account, all feature requests and bug reports from forums are still considered and checked by the maintainers.
You might need to run the installer as Administrator. If this does not help, try installing MCreator from ZIP.
Make sure that you don't have Antivirus that could be blocking MCreator too.