XP Service Pack 3 installation blues

svcpack.log had following entries around the failure

115.250: IsSPBetaKey:CoCreateInstance Failed: 0x80040154
115.734: Trying CheckVLKForBlock again
116.140: Error: CheckVLKForBlock failed
116.140: Inventory complete: ReturnStatus=536753847, 87672 ticks
116.140: Num Ticks for invent : 87672
116.750: UnRegisterSpuninstForRecovery, failed to delete SpRecoverCmdLine value, error 0x2
116.750: DoInstallation: Failed to unregistering spuninst.exe for recovery.
116.750: The requested lookup key was not found in any active activation context.
148.437: Message displayed to the user: The requested lookup key was not found in any active activation context.
148.437: User Input: OK
148.437: Service Pack 3 installation did not complete.
150.312: Message displayed to the user: Service Pack 3 installation did not complete.
150.312: User Input: OK
150.312: Update.exe extended error code = 0x1ffe36b7
150.312: Update.exe return code was masked to 0x643 for MSI custom action compliance.

After further searches Microsoft Support Article 949377 pointed me to install and use subinacl to reset access permissions on various registry locations and files by running the following

cd /d "%ProgramFiles%\Windows Resource Kits\Tools"
subinacl /subkeyreg HKEY_LOCAL_MACHINE /grant=administrators=f /grant=system=f
subinacl /subkeyreg HKEY_CURRENT_USER /grant=administrators=f /grant=system=f
subinacl /subkeyreg HKEY_CLASSES_ROOT /grant=administrators=f /grant=system=f
subinacl /subdirectories %SystemDrive% /grant=administrators=f /grant=system=f
subinacl /subdirectories %windir%\*.* /grant=administrators=f /grant=system=f
secedit /configure /cfg %windir%\repair\secsetup.inf /db secsetup.sdb /verbose

I cringed as various keys and files got touched by the script and ran SP3 installation again. This time it completed successfully. While it was nice to be done with the install,  this is bit of a whodunit mystery made unsolvable by destruction of all forensics by subinacl.