SQL SERVER If the uninstallation is not clean, it will cause the next installation failure, the following is the steps to uninstall, I tried many times, can be completely uninstalled clean. Of course, some of the following steps may be omitted.
1. Stop all SQL SERVER 2008 related services
2. In the Control Panel "Add Remove Programs", remove the SQL SERVER 2008 related programs
3. Uninstalling the SQL 2008 components with the Windows Install clean up tool
4. Delete all SQL services with SrvInstw.exe
5. Clear the Registration form
5.1 Remove all HKEY_CURRENT_USER---software----Microsoft SQL Server folders under Microsoft
5.2 will HKEY_LOCAL_MACHINE---software---Microsoft SQL Native Client under Microsoft, Microsoft SQL Server, Microsoft SQL Server redist All Delete
6. Delete residual files
7. Remove the Microsoft SQL Server folder under the SQL Server installation path, such as: C drive--program file
8. Restart your computer
[Reprint] How to completely uninstall SQL SERVER clean