During the SQL Server Service Pack installation, "Consistency validation for SQL Server registry keys" failed.

Description:

Issue: Installation of SQL Express 2008 fail with the error: "Consistency validation for SQL Server registry keys" failed

Error:
Rule "Consistency validation for SQL Server registry keys" failed
The SQL Server registry keys from a prior installation cannot be modified. To Continue; see SQL Server Setup documentation about how to fix registry keys.

Solution-1:

Navigate to:
%ProgramFiles%\Microsoft SQL Server\100\Setup Bootstrap\Log

Search (in Detail_GlobalRules.txt) for lines containing:
"could not fix registry key"

Run regedit

Set full control permissions for the appropriate registry keys mentioned in "Detail_GlobalRules.txt" file.

Re- run the installation.


Solution-2

Steps
1. Located HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server in registry
2. Right click and go to Permission
3. Click on Advance
4. Tick on both check box
     I. Inherit from parent the permission...
    II. Replace permission entries on all child objects..., click OK
5. Click OK again