SQL Server 2005 requires that the SQL Server user groups match the corresponding security IDs in the Windows registry to successfully install /update or uninstall SQL Server 2005.
To work around this problem, follow these steps:
Start Registry Editor, and then locate one of the following registry subkeys:
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMicrosoft SQL ServerMSSQL.2005Setup
Note Only one of these registry subkeys will exist on your computer.
Empty the following registry entries: