You are correct. There is an internal flag that is set that designates a file as a "Toolbox" part.
Luckily, SolidWorks includes a utility to set (and UNSET) this flag.
The utility is located in the directory:
C:\Program Files\SolidWorks\Toolbox\data utilities
and is called:
sldsetdocprop.exe...
"Error code 1720" can be a nightmare to try and troubleshoot. They can occur during install and uninstall attempts and can be extremely frustrating.
The solution is to trick Windows & the Windows Installer into thinking the application is not installed.
To do this, you will need to delete a...