Microsoft Knowledge Base Article 921181 contains the following INTRODUCTION:
This article describes an update that you can apply to add the following two new features to a Microsoft Windows Server 2003 Service Pack 1 (SP1)-based server cluster or to a Windows Server 2003 R2-based server cluster:
• File share witness
• Configurable cluster heartbeats
Although these two features are contained in the same update package, these two features are both separate and independent from each other.