It his very useful to provide a valid repair path to an MSI software in order to allow automatic repair capability of Windows Installer.

Here's where to go in your registry:

HKEY_LOCAL_MACHINE\SOFTWARE\Classes\Installer\Products

Select your software key: Ex.\Products\1C5C0DF1B10BC4B469705E3D3B1D13F8

Go in this subkey: \SourceList\Net

Then add a path in string "1" where the MSI can be found:

Ex.c:\program files\microsoft intellipoint 4.1\mouse\Setup

Windows Installer automatic repair capability his now enabled for your MSI software.