cd %drive%\Program Files\Update Services\Tools
wsusutil reset
To re-install WSUS with a clean database ie no previous configuration;
Run Windows Powershell as Administrator and use the following commands:
Uninstall-WindowsFeature -Name UpdateServices,Windows-Internal-Database -Restart
Post restart, delete EVERYTHING in the "C:\Windows\WID" (for Win 2012 r2) folder, then run the following command to re-install WSUS:
Install-WindowsFeature UpdateServices -Restart
This only works on Powershell 3 or higher. More info here: https://technet.microsoft.com/en-us/library/cc732257.aspx
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