I have just had this error

"The following error has occurred:
Attempted to perform an unauthorized operation.
Click 'Retry' to retry the failed action, or click 'Cancel' to cancel this action and continue setup."

This failed to work for both SQL 2008 R2 and SQL 2012 Express installations, I had previously disabled the Anti Virus which was Bullguard but had to subsequently completely uninstall the Anti Virus software. Once this had been removed the SQL software installed perfectly.