The error message "CorelPainter11_SP1 can't be installed on this disk. Corel Painter 11 is not present on the volume." is shown when installing SP1 for Painter 11.
To resolve the error message, perform a clean reinstall of the original Painter 11 application, then immediately run the update patch.
Remember to back up the Painter 11 Users folder and any custom Painter resources to a different location prior to reinstallation.