Windows Update has downloaded an update but is unable to install it. It creates a system restore point but then displays a message:
Some updates were not installed.
Failed: 1 update
Code9370001 Windows update encountered an unknown error
I found the following information from update history about the update it's trying to install:
System Update Readiness Tool for Windows Vista (KB947821) [September 2009]
Download size: 319 KB
You may need to restart your computer for this update to take effect.
Update type: Important
This tool is being offered because an inconsistency was found in the Windows servicing store which may prevent the successful installation of future updates, service packs, and software. This tool checks your computer for such inconsistencies and tries to resolve issues if found.
Help and Support: