helps to uninstall sql 2005 and 2008 in unattended and silent.
I have not the name of the instances
does not work
C: \ Program Files \ Microsoft SQL Server \ 90 \ Setup Bootstrap \ ARPWrapper.exe / Remove
"%ProgramFiles%\Microsoft SQL Server\100\Setup Bootstrap\SQLServer2008R2\x86\setupARP.exe" /ACTION="UNINSTALL"
I think you need to use /q but you'll have to write a script to identify and pass in the instance names to /INSTANCENAME=