Upgrading Vista while running Server as a service
TAC Vista Server
The installation directories include the version number (i.e. C:\Program Files\TAC\TAC Vista 4.2.3). If you perform an upgrade before unregistering the service, you will be unable to unregister the service unless you reinstall the previous version to provide the files Windows requires.
If a user is running Vista Server as a service it is recommended that the user unregister the service before performing an upgrade.