Depending on the environment, the upgrade to SQL Server 2008 can be complex, particularly when technologies such as replication and clustering are involved. In this section, rather than attempt to cover all of the possible upgrade issues, I've aimed for the more modest task of providing you with an insight into the various upgrade techniques.
SQL Server 2008 Upgrade Technical Reference Guide
As with installation, upgrading to SQL Server 2008 requires considerable planning and preparation. Microsoft recently released the SQL Server 2008 Upgrade Technical Reference Guide. Weighing in at 490 pages and available for free download from the Microsoft website, this guide is essential reading as part of any upgrade ...