For a possible answer, see “Upgrading SharePoint Products and Technologies for Team Foundation Server” at http://msdn.microsoft.com/en-us/library/bb909691.aspx.
The documentation covers two common scenarios:
- Upgrading to Windows SharePoint Services 3.0
- Upgrading to Microsoft Office SharePoint Server 2007
Remember that you can add your annotations, your feedback and your comments to the MSDN content these days. Scroll to the bottom of the page and ‘collaborate’ q;-)