Have you encountered error 0x84B30002 when uninstalling MSSQL 2008 R2, preventing the uninstall from proceeding? I have. So far I have only encountered the issue with Express Edition, although rumor has it that the error can occur with other editions as well. The error message will be displayed in a pop-up as well as the summary.txt log file in the installation directory.
Here is how to fix it:
Launch the registry editor by typing regedit in the Run bar in the start menu. Navigate to the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\
Here is how to fix it:
Launch the registry editor by typing regedit in the Run bar in the start menu. Navigate to the following registry key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\
After expanding uninstall, you will need to locate each key related to the SQL instance you are attempting to remove - if there is only one instance on the server, locate each key with the word SQL in the DisplayName field.
Within each key, locate the GUID. It will look something like this: 234A1B2C-12AB-1AB2-B1C2-A12B345678C1 and be typically contained in either the ModifyPath or UninstallString fields.
Take each GUID, and use msiexec to manually force the uninstall from the command line like so:
msiexec /x "{234A1B2C-12AB-1AB2-B1C2-A12B345678C1}"
Replace that string with the relevant GUID, and run the command for each GUID you have. You can automate the process a bit by dumping the list into a .bat file. When running the command, a window prompt may appear asking if you wish to proceed with uninstallation - just go ahead and authorize the uninstall where it appears.
Once completed, you can double check the registry key where we initially found the GUID's to ensure everything has been removed. I have been forced to do this a few times now and have yet to encounter any further issues, though. After you have run these commands, you should be all set to install a new instance of MSSQL.