This step-by-step article describes how to determine whether a security update supports HotPatching, how to set up an environment to test HotPatching, and how to install security updates that use HotPatching.
If you use HotPatching, you can install General Distribution Release (GDR) security updates on servers that run 32-bit versions of Microsoft Windows Server 2003 Service Pack 1 (SP1), without restarting the servers.
Source : Microsoft Technet KB
