Installation Error

I tried to update my itunes to version 11.1.4, but I got the error "The installer has encountered an unexpected error installing this package. This may indicate a problem with this package. The error code is 2721."

The Apple support general troubleshooting says to empty the temp folder, then uninstall itunes and reinstall it. I emptied the temp folder, but then when I tried to uninstall itunes, I got the same error message.

I performed a clean boot and tried uninstalling again, and I am still receiving the error message. I have made sure Windows is completely updated, and I have also tried restoring Windows to a previous point.

I am completely lost at this point.