Yes, you need to install the SP2 upgrade for WSS v3 before you run the SP2 installer for MOSS 2007. You don't have to run the Configuration Wizard to finalize the installation until you're done installing the MOSS updates, but you definitely need to install
the WSS bits on the server before you do the MOSS bits.
John
MCITP and MCTS: SharePoint, Virtualization, Project Server 2007
My books on Amazon:
The SharePoint 2010 Disaster Recovery Guide and
The SharePoint 2007 Disaster Recovery Guide.
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My Central Admin.