JSI Tip 5086. How do I patch a software installation stored on a network server that is deployed using Microsoft Software Installer?

Microsoft Knowledge Base Article 226936 contains the following summary:

When a network share contains a software installation that is used with Active Directory for assigning and publishing programs, it may be necessary to apply update patches to the software. These patches are identifiable by having an .msp file name extension. This article describes how to patch such a software installation.