This problem occurs because the SQL Server user groups do not match the corresponding security IDs in the Windows registry.
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.
Solution
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
HKEY_LOCAL_MACHINESOFTWAREMicrosoftMicrosoft SQL ServerMSSQL.XSetup
Note Only one of these registry subkeys will exist on your computer.
Empty the following registry entries:
SQLGroup
FTSGroup
AGTGroup
FTSGroup
AGTGroup
Exit Registry Editor.
Install update , Happy Patching 🙂