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.