The following is the official Microsoft releases SQL2008 removal method
Issues that should be considered before uninstalling a standalone SQL Server 2008 instance
•We recommend that you uninstall SQL Server in Control Panel using the Add or Remove Programs feature.
•For computers running SQL Server 2008 with earlier versions of SQL Server, Enterprise Manager and other programs that rely on SQL DMO may be disabled. This problem may occur if:
◦Uninstall any combination of Microsoft SQL Server 7.0 through SQL Server 2008, SQL Server 2000 and one or more of these instances installed in parallel
◦SQL Server 2008 installed in parallel and after SQL Server 2008
This problem occurs after the SQL Server SQL DMO COM library is registered.
To re-enable Enterprise Manager and other programs with SQL DMO dependencies, register SQL DMO. To do this, open a command prompt, type the following command, and press enter:
Copy the codeThe code is as follows:
•Before deleting SQL Server components on your computer, make sure that the size of the page file is sufficient. The size of the page file must be twice the size of the physical memory. Insufficient virtual memory may cause SQL Server to be not completely deleted.
•In SQL Server 2005, SQL Server browser integration installation is installed with the Database Engine or Analysis Services.
In SQL Server 2008, the SQL Server browser automatically performs a separate installation of the database engine with Analysis Services. If you have multiple instances of SQL Server 2008, the SQL Server browser will automatically uninstall when the last instance of SQL Server 2008 is uninstalled.
However, if SQL Server 2005 exists in one or more instances of SQL Server 2008 and in the system, the SQL Server 2008 browser does not automatically delete the last instance of SQL Server 2008. The SQL Server 2008 browser has SQL Server 2008 installed on the system that keeps easy to connect to.
You can keep the SQL Server 2008 browser installed with SQL Server 2005. The SQL Server 2008 browser will continue to work properly.
To uninstall all components in SQL Server 2008, you must uninstall the SQL Server 2008 browser components by using the Add or Remove Programs feature in Control Panel. If you delete a SQL Server 2005-named instance of SQL Server 2008 browser, connection to SQL Server 2005 may be interrupted. In this case, you can reinstall the SQL Server 2008 browser by using one of the following methods:
◦Repair instances of SQL Server 2005 by using the Add or Remove Programs feature in Control Panel.
◦Instances that install SQL Server 2005 database engine or Analysis Services.
Actions performed before the SQL Server 2008 instance to be uninstalled
•Back up your data
You may have to save the database in its current state. You may want to save changes made to your system database. In both cases, make sure to back up the data before uninstalling SQL Server. Alternatively, save a copy of all data and log files to a folder outside the MSSQL folder. (To the MSSQL folder will be deleted during the uninstall process.
The files you must save include the following database files.
Note These files will install part of SQL Server.
◦Distmdl.*
◦Master.*
◦Mastlog.*
◦Model.*
◦Modellog.*
◦Msdbdata.*
◦Msdblog.*
◦Mssqlsystemresource.*
◦Northwind.* (This database is an optional installation).
◦Pubs.*
◦Pubs_log.*
◦Tempdb.*
◦Templog.*
◦Report Server [$Instance Name] (This file is the default database for reporting services).
◦Report Server [$Instance Name] TempDB (This file is the default database for temporary reporting services).
•Delete local security group
Before uninstalling SQL Server, delete the local secure group of SQL Server components.
•Save or rename the report service folder
If you use SQL Server to install and report services, save or rename the following folders and subfolders:
◦Drive: \Microsoft SQL Server\MSRS10. SQL Server instance name\Reporting service
Remark
◦In these files, the drive is a placeholder for the drive on which SQL Server 2008 is installed.
◦If you use the SSRS configuration tool to configure the installation, the name may be different from the name in this list. Additionally, the database may be located on a remote computer running SQL Server 2008.
•Delete the virtual directory of the report service
Use Internet Information Services (IIS) Manager to delete the following virtual directories:
◦Report Server [$Instance Name]
◦Report [$Instance Name]
•Delete the report server application pool
Use IIS Manager to delete the report server application pool.
•Stop all SQL Server services
We recommend that you stop all SQL Server services before uninstalling SQL Server components. Active connections prevent successful uninstallation.
•Use an account with appropriate permissions
Log in to the server by using a SQL Server service account or by using an account with equivalent permissions. For example, you can log in to the server using an account that is a member of the local administrators group.
How to uninstall an instance of SQL Server 2008
Note that the SQL Server installation program is a complicated process. The SQL Server installer modifies registry keys and DLL files a lot. The SQL Server installer also installs and updates permissions items and services registrations.
We test the SQL Server installer process in multiple configurations, when installing and uninstalling. However, we cannot test the number of changes that all configuration third-party products and specific customers can make at the operating system level. Therefore, you may encounter rare cases where SQL Server is prevented from successfully installing or uninstalling the installer used.
These complex issues are because the SQL Server Support Team may recommend that you help reinstall the operating system if you do not perform a clean uninstall of SQL Server programs. This helps provide a clean platform to reinstall SQL servers on your system.
1. Please follow the following steps to determine the version of the Windows server you are running:
Windows 2008 Server
a. Open the program and function items in the control panel. To do this, click Start, type , in the Start Search box, and then click Programs list.
b. In the list of currently installed programs, click Microsoft SQL Server 2008, or click Microsoft SQL Server 2008 (64-bit).
c. Click Uninstall. The SQL Server Installation Wizard will start.
Windows Server 2003
a. Open the Add or Remove Programs item in the Control Panel. To do this, click Start, click Run, type , in the Open box, and then click OK.
b. In the list of currently installed programs, click Microsoft SQL Server 2008, or click Microsoft SQL Server 2008 (64-bit).
c. Click Delete. The SQL Server Installation Wizard will start.
2. In the Component Selection-Uninstall page, select a server or the component you want to delete shared.
Click the Report button to view a list of SQL Server components and installed features. The report includes version information, version information, update level information, and language information for each installed component and feature.
3. Click Next.
4. On the Confirm-Uninstall page, view the components and features that will be deleted, and then click Next list. The installation progress page will display the status of the installer.
5. On the Completed Installation page, click Finish to exit the Installation Wizard.
6. Repeat steps 2 to 5 until all SQL Server 2008 components are deleted.