Can't re-install Microsoft SQL Server 2008 R2 with Default Instance

Question

I installed MS SQL Server 2008 R2 and I named my default instance "MSSQLSERVER". I want to uninstall that instance and start over. I used the Programs and Features control panel to completely remove MS SQL Server but when I run the installer again, the "MSSQLSERVER" instance remains. I know I can just create a new instance and call it something else but it bugs me that I didn't completely remove it.

I have searched the MS KB for information on removing MS SQL Server and everything I've found so far indicates that all I have to do is to use the Programs and Features control panel.

Can someone explain to me how to remove this instance or, if it's not possible, why not?

Answer 1

Looks like a failed uninstall. Try the following command line option to manually uninstall the instance:

At a command prompt, type the following command, and then press ENTER:

CD %ProgramFiles%\Microsoft SQL Server\100\Setup Bootstrap\Release

Type the following command, and then press ENTER:

setup.exe /ACTION=uninstall /FEATURES=SQL /INSTANCENAME=MSSQLSERVER

Reference http://support.microsoft.com/kb/955404

If this doesn't work, let me know; there are some other ways we can try...