For one of my client a tech went on site to upgrade SQL and things didn't work the next day. After looking into it I had thought he had just installed SQL server 2008 R2, but not upgraded any instances or the Management Studio. So I fixed the management studio and upgraded that.
Then I ran SQL 2008 Express Edition with advanced Services again and choose to upgrade from 2005. The Rule Check failed on "Previous version"
After digging through forums and looking at other peoples similar issues there appear to be some registry keys. When I was looking into this I realized there is an entry for "MSSQL10_50.instance" and it shows the old 2005 database that it upgraded from etc. However this instance doesn't actually exist so I'm guess this is the failed previous upgrade. The original 2005 database is running and working.
I'm wondering if I can delete the entire Registry folder for teh failed instance and the directory with all the files for it and try again. Would that clear the failed previous upgrade? or would it cause complete Chaos of some kind I don't know.
Thanks in advance.