Incorrectly modifying a Product Code can break your application's upgrade path, leading to duplicate installations or orphaned registry keys. Follow these strict deployment rules: Maintain the Product Code when:

Knowing when to change this GUID is the secret to a smooth deployment. 1. Major Upgrades (Change Required)

What specific are you trying to resolve?

Error: "Another version of this product is already installed"

32-bit and 64-bit versions of the same application must always have different Product Codes. How to Find or Set the Product Code

For smaller changes, like patches or minor version updates (e.g., from 1.0 to 1.1), you typically keep the Product Code unchanged. Instead, you would change only the Package Code and, for a minor upgrade, increment the ProductVersion property.

InstallScript MSI projects handle properties similarly to Basic MSI projects. You can view the GUID under , but the InstallScript engine also accesses it at runtime using the system variable PRODUCT_GUID . In Pure InstallScript Projects

Select and click on General Information .

Error: "Another version of this product is already installed"

Identifies a specific release of an application. It changes between major versions (e.g., version 1.0 to 2.0) but remains identical across identical builds.

: In some licensing scenarios, the product code can be used to identify the software for which a license is required.