I had uninstalled this officeserver and installed SQL 2008 express for a demo server.
While there are some other solution available on this error: I fixed it by changing a different registry
Here it is:
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Shared Tools\Web Server Extensions\12.0\EvaluatorProvisioning\DatabaseEngine]
Changed the ServiceName value to the new SQL Express instance and Config Wizard started to work again...