Upgrading to SQL Server 2008 – Technical Reference Guide
A common request from customers is for information about upgrading from SQL Server 2000/2005 to SQL Server 2008.
In conjunction with Solid Quality Mentors, Microsoft has published a great technical reference guide covering most upgrade scenarios. At almost 500 pages you better hope it does :).
Following is the link to the whitepaper:
This should be read in conjunction with the Books online guidance on this subject: