During the Organization Preparation stage of an Exchange 2013 install or uninstall, you may get the below error message:
An error occurred with error code ‘3221684226’ and message ‘The system cannot find the file specified.’
This error message is not very descriptive but the issue is that the AD tools are not installed on the Exchange server.
To install these, run the below command in an elevated PowerShell window:
Install-WindowsFeature RSAT-ADDS
Once done, you can re-run your install or uninstall operation.