Orca.exe is a database table editor for creating and editing Windows Installer packages and merge modules. The tool provides a graphical interface for validation, highlighting the particular entries where validation errors or warnings occur.
This tool is only available in the Platform SDK Components for Windows Installer Developers. It is provided as an Orca.msi file. After installing the Platform SDK Components for Windows Installer Developers, double click Orca.msi to install the Orca.exe file.
I'm posting just the orca.msi file because it's a pain to download the whole SDK. This tool is useful for working w/ MSIs