Note about install and upgrade SQL 2008

- Cross-version instances of SQL Server 2008 are not supported. Version numbers of the Database Engine, Analysis Services, and Reporting Services components must be the same within an instance of SQL Server 2008.

- Before upgrading SQL Server, enable Windows Authentication for SQL Server Agent and verify that the SQL Server Agent service account is a member of the SQL Server sysadmin group.

- Before upgrading from one edition of SQL Server 2008 to another, verify that the functionality you are currently using is supported in the edition to which you are upgrading.

- Cross-platform upgrade is not supported. You cannot upgrade a 32-bit instance of SQL Server to native 64-bit. However, you can upgrade a 32-bit instance of SQL Server to the WOW64: the 32-bit subsystem on a 64-bit server. You can also back up or detach databases from a 32-bit instance of SQL Server, and then restore or attach them to an instance of SQL Server (64-bit) if the databases are not published in replication. In this case, you must also re-create any logins and other user objects in master, msdb, and model system databases.

Note That !:

- The Developer Edition contains the same functionality as Enterprise Edition, but is restricted, by the license, to testing and development only.

- Windows Essential Business Server Premium Edition® (which will replace Small Business Server®) comes with a license for SQL Server 2008 Standard Edition®.

- SQL Server 2008 Web Edition enables hosting companies to provide low cost, highly scalable hosting for developers, SMBs, and consumers, all with a low monthly licensing fee, four CPU support, and no limits on memory and database size for increased scalability.

To upgrade to SQL Server 2008, you must be running a supported operating system.

- The installer will check a number of conditions and block the upgrade if certain conditions are not met:
- Upgrade will be blocked if there is a pending restart.
- Upgrade will be blocked if the Windows Installer service is not running.
- Upgrade will be blocked if performance counters are corrupt.

To upgrade an instance of SQL Server to a SQL Server failover cluster,

the instance being upgraded must be a failover cluster. To upgrade a stand-alone instance of SQL Server to a SQL Server failover cluster, install a new SQL Server failover cluster and then migrate user databases from the stand-alone instance by using the Copy Database Wizard.

More Links

- For more information about Preparing to Install SQL Server 2008, see "Version and Edition Upgrades", http://go.microsoft.com/fwlink/?LinkID=127393

- For more information about Preparing to Install SQL Server 2008, see "SQL Server 2005 Features Comparison", http://go.microsoft.com/fwlink/?LinkID=127394

- For more information about Preparing to Install SQL Server 2008, see "Windows Essential Business Server Overview", http://go.microsoft.com/fwlink/?LinkID=127395


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main source : 6231A Maintaining a Microsoft SQL Server 2008 Database

What is WoW64 ?

WoW64 (Windows 32-bit On Windows 64-bit) is a subsystem of the Windows operating system that is capable of running 32-bit applications and is included on all 64-bit versions of Windows — including Windows 2000 Limited Edition, Windows XP Professional x64 Edition, IA-64 and x64 versions of Windows Server 2003, 64-bit versions of Windows Vista and Windows Server 2008, as well as the 64-bit edition of Windows 7. In Windows Server 2008 R2 Server Core, it's an optional component. WoW64 is designed to take care of many of the differences between 32-bit Windows and 64-bit Windows, particularly involving structural changes to Windows itself.

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main source : http://en.wikipedia.org/wiki/WoW64