At a command prompt, run the following command:
"%ProgramFiles%\Microsoft SQL Server\90\Setup Bootstrap\ARPWrapper.exe /Remove"
Uninstall the SQL Server components one at a time until all the SQL Server components are uninstalled.
Note Add or Remove Programs also runs the ARPWrapper.exe program by using the /Remove option. However, the reference to the ARPWrapper.exe program may have been deleted.
If you have uninstalled SQL Server Reporting Services, you must perform the following tasks: • Delete the Reporting Services virtual directories
Use Microsoft Internet Information Services (IIS) Manager to delete the following virtual directories: • ReportServer[$InstanceName
• Delete the ReportServer application pool
Use IIS Manager to delete the ReportServer application pool.
You can check the link http://support.microsoft.com/kb/909967