All you need to know to deploy software updates (hotifx, patch) to SharePoint 2007

Installing software updates for WSS 3.0 is not like installing on a Window Server role. For one, all the servers in a WSS 3.0 needs to be in sync with the latest binary changes that an update may have.

Even in a single server applying a hotfix involves other tasks like executing the Configuration Wizard.
http://technet.microsoft.com/en-us/library/cc288269.aspx

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