Upgrading 2007 Editions
Upgrading between SharePoint 2007 editions is straightforward. There are only a couple of issues worth mentioning, included here in the interest of completeness.
To upgrade from WSS 3.0 to MOSS:
Run OfficeServer.exe. The setup process installs the additional web parts, templates, and services. See Chapter 13 for information about installation options.
Once MOSS is installed, you may want to replace your top-level web site with a new site based on the Collaboration Portal site template, which is the default template for most MOSS installations. To do that:
Copy the existing top-level site collection to a new location.
Navigate to the Central Administration site and click Application Management → Delete Site Collection to delete the existing top-level site collection.
Click "Create site collection" and create a new top-level site collection using the Collaboration Portal template found on the Publishing tab of the site template list.
Create the new top-level site collection from Central Administration.
To upgrade from MOSS Standard Edition to Enterprise Edition:
Navigate to the Central Administration site and click Operations → Enable Enterprise Features under the Upgrade and Migration heading.
Select Enterprise and click OK.
Setup installs the full version MOSS no matter which edition you initially choose. The features are simply enabled or disabled based on your license key.
If you need to uninstall SharePoint from a server that has both WSS 3.0 and MOSS installed, you ...