In a recent case, a customer reported error 1603” during installation. As I’ve mentioned many times in various places, error 1603 is a generic error code that doesn’t tell us much. So, you can either apply some generic troubleshooting (reboot, check download, disable UAC, reinstall VC++ manually, …) or check the detailed installation logs for more specific information.

The problem is this specific case was that the installer wasn’t able to update ProductInformation.pit. Without looking at the logs, I don’t know whether you would ever figure this out.