To begin the actual upgrade process, click the Installation link in
the navigation pane on the left side of the SQL Server Installation
Center. This will display the Installation page, which you can see in
Figure 2. On that page, click the Upgrade from SQL Server 2005, SQL
Server 2008 or SQL Server 2008 R2 link to launch the SQL Server 2012
SQL Server 2012
from the Installation
Page of the SQL Server
As with a clean installation, the first thing the SQL Server 2012
installation wizard does is run the Setup Support Rules to check if
there are any system problems that would interfere with the upgrade.
Figure 3 shows the Setup Support Rules dialog box, with the Show
Details option enabled.
If any problems are detected that will prevent the upgrade from
running, they’ll be displayed in the rules list preceded by a yellow
icon. In addition, the status will be listed as Fail. You must correct
any detected problems before you can continue the upgrade process.
If the system passes all of the setup rules, the OK button will be
enabled. Clicking OK from the Setup Support Rules dialog box displays the Product Key dialog box shown in Figure 4. You can install
the free Evaluation edition, or you can enter your SQL Server 2012