To perform an in-place upgrade of SQL 2005 Evaluation edition to other SQL Server full blown editions, simply run the setup and it will identify the existing installation, and will run an upgrade check. It will then let you know if the upgrade is possible or not. If the upgrade is possible, simply go through the setup wizard and it will automatically upgrade the already installed instance of evaluation edition.
Upgrading from Evaluation Edition 2005 after it has expired is a different story entirely
Now, this becomes a little tricky. You have to first uninstall SQL 2005 Eval edition and then install the full blown edition on the machine.
In case you want to keep the existing databases, you can use the SAVESYSDB parameter at command prompt. For more information on this, refer to KB 914158...
If You receive an error message when you try to upgrade an expired installation of SQL Server 2005 Evaluation Edition to a retail version of SQL Server 2005
his problem occurs because the Setup program cannot start the SQL Server service. When you install retail versions of SQL Server 2005, the Setup program tries to start the SQL Server service of the old installation of SQL Server 2005 Evaluation Edition. However, the service cannot start because the installation is expired. Therefore, the installation stops, and you receive the error messages.
To work around this problem, you must uninstall SQL Server 2005 Evaluation Edition. Then, install the retail version of SQL Server 2005. If you want to keep system databases and reuse the databases after a new installation, you can uninstall SQL Server 2005 at the command prompt by using the SAVESYSDB parameter. Then, install the retail version of SQL Server 2005 at the command prompt by using the USESYSDB parameter.
When SQL Server 2005 Evaluation Edition is expired, you cannot start the SQL Server service. If you want to move the user database to the retail version of SQL Server 2005, you can copy the user database files to a specified location. Then, you can attach the database to the retail version of SQL Server 2005.
For more information about how to install SQL Server 2005 at the command prompt, visit the following Microsoft Developer Network (MSDN) Web site:
In case you are still running SQL 2000 Eval edition (I would doubt that), you can refer to KB 281574 for steps on how to upgrade the same to a full blown edition of SQL 2000.