ProductCode
This variable contains the product code that you enter in the Product GUID field on the Product info project page. This unique product code is used by all installers to identify the product on the target system, and is also used as part of folder names and registry keys for product-specific information.
Usage
Used internally by all installers. You can refer to this variable as <ProductCode>. Do not set this variable directly; it is set automatically when you build the installer, using information from the Product info project page.