I am not sure if it is a symptom of my advanced age, but I am forgetting more and more.  I know that you can't do an inplace upgrade from a 32-bit version of SQL 2005 to a 64-bit version, but I did indeed forget.   I am running into this issue more frequently on SQL 2008 upgrades than I did with previous version, becuase SQL 2008 offers Workgroup Edition 64-bit for the first time.  Many of the customers running Workgroup Edition SQL 2005 in a WOW configuration are looking to upgrade.   

The only workaround that I knowis to:

• Script out logins, jobs, and any objects that are stored in MSDB and Master
• Detach user databases
• Uninstall 32-bit version of  SQL Server
• Reboot Server, just to be sure
• Install 64-bit version of SQL Server
• Create logins, jobs and other server wide objects
• Re-attach user databases