If you are the developer or packaging engineer, you can find (or change) the code easily within the InstallShield interface: Open your InstallShield project ( .ism file).
For "Small Updates" or "Minor Upgrades," the Product Code must remain the same. For a "Major Upgrade" (where the old version is completely uninstalled first), the Product Code change. How to Find Your Product Code in InstallShield installshield product code
The Product Code dictates how Windows Installer handles your package: Major Upgrades If you are the developer or packaging engineer,
Think of it like a Social Security Number for your software: installshield product code
If you are a system administrator trying to automate a deployment, you can find the Product Code of an already installed app using : powershell