Windows Update KB935509 Failed

A lot of users have a problem with windows update KB935509 failing in Windows Vista Enterprise and Ultimate editions. A bigger issue with this is without this update you cannot install Vista Service Pack 1.

I had this same issue and I found a way to install this update.
It took a while because all the basic suggestions didn't help. I do not have the Comodo firewall or any other applications which would interfere with the update.

First let me list what did not work for me (which is basically 100% of the suggestions currently posted on the web)
These solutions did not work - don't waste your time trying this....
- Download stand alone installer (did not work)
- Disable system protection and install update in Safe Mode (did not work)
- Disable firewall and uninstall anti virus then try the update again (did not work)
- Repair windows fixboot file (did not work)

Ok, so here is what I did that finally fixed the issue
1. I ran sfc /scannow (run it through the command prompt as an administrator)
2. I downloaded and installed the BitLocker Drive Preparation tool:
http://www.microsoft.com/downloads/details...&displaylang=en
3. After you install this update, open the BitLocker Drive Preparation tool and run the wizard. The tool will be located in Start > All Programs > Accessories > System Tools >BitLocker
4. Reboot the computer after the BitLocker tool finishes and prompts you to do so.
5. Try the KB935509 update again

Hope that helps