SQL setup fails to update - installer cache is missing files

installing the service pack you are receiving the following error message:

a link to correct this problem can be found here but still it is quite tricky.

You can download a file, FindSQLInstalls.vbs to gather the details of your SQL Server  installation. I had errors running the file at first , removing the comments at the top of the file solved the issue.

Mostly I found errors relating to missing path, both the original cd that was copied in a directory, and directory created  by the SQL server setup that were missing like d:\6e712df430a776566d80fe027ca507.

recreating the file to the original setup cd on the disk was mandatory, I tried to recreate the setup directory above (d:\6e712df430a776566d80fe027ca507) as a shortcut for the setup to relink source and destination files within  the c:\windows\installer directory, but the latter did not work.

I didn't have to copy all the files listed in the one created by the vbs script - I relaunched the Setup 4-5 times, looked for the missing files in the .txt file and finally went through the SP3 setup normally.

Steps:

1. Go to http://support.microsoft.com/kb/969052 and download the FindSQLInstall.vbs script
2. Using a command prompt (elevated privileges), run  Cscript FindSQLInstalls.vbs %computername%_sql_install_details.txt
3. open the text file to view the details.
4. Recreate the path to the original setup cd if required
5. Try to rerun setup and look in the text file for the missing file, copy it in the %windir%\installer directory (serveral trials may be required if serveral files are missing as in my case)