When trying to install MOSS 2007 SP2, you receive this error:
Windows SharePoint services 3.0 Service Pack 2 is not installed. Microsoft strongly recommends that you install Windows SharePoint Services 3.0 Service Pack 2 before installing this update. Do you want to go to the Microsoft Download Center, where you can download Windows SharePoint Services 3.0 Service Pack 2?
Check your Add or Remove Programs and Show Updates. You may have some WSS installed under the Microsoft Office SharePoint Server 2007. Most of these cannot be uninstalled.
In my case, I had a WSS hotfix KB941422 (as required by a third party application) installed as shown below: