When installing MySQL 5.5 on a Windows 7 machine, I received this error: "an unknown error occurred while validating the service account" and the installation would not complete, and I also got a configuration error with something like "unable to configure service". After googling a bit and playing around with the settings, the answer was pretty simple. The default administrator account needs to be enabled . Although this was a pretty easy answer, I couldn't find it anywhere! Result after enabling the default administrator account Sorry I don't have more screen-shots, but I think it's pretty self explanatory. I may or may not add more later.