I successfully upgraded SQL 2005 Express (32bit) to SQL2008 R2 Express (32bit) for a mini Veeam environment. I then wanted to upgrade Studio Management but got the following error:
Rule "SQL Server 2005 Express tools" failed
The SQL Server 2005 Express Tools are installed. To continue, remove the SQL Server 2005 Express Tools.
First of all I removed the SQL server 2005 remnants from the Programs and Features but that had now affect.
I then removed the registry key:
Go to HKEY_LOCAL_MACHINE -> Software -> Microsoft -> Microsoft SQL Server . Right click "90" and then select delete