A new tool is being offered through Windows Update; the System Update Readiness (SUR) Tool. It is designed to help diagnose and fix issues that are preventing Windows updates or Service Packs from installing correctly. According to the documentation it is only offered to systems that are experiencing one of the conditions that the tool could resolve. (How it can determine this without first running is beyond me.) The tool runs on Windows Vista, Windows Server 2008, Windows 7 and Windows Server 2008 R2. Like the monthly Windows Malicious Software Removal Tool (WMSRT), it runs a onetime scan of your system to determine if it is experiencing one of the issues it can detect and fix. A log of this activity is written to %SYSTEMROOT%LogsCBSCheckSUR.log. As of this writing the tool is presented in Windows Update as System Update Readiness Toll for Windows 7 for x64-based Systems (KB947821) [February 2011]. This leads me to beleive that it will be updated and offered in new “versions” further on.
You can also download the tool manually and run it, check the first link below.
On one system I experienced an error when trying to install Windows Server 2008 R2 Service Pack 1; An unknown error has occurred; error code 0x800f0818. I ran the SUR Tool and it detected an error in the %SYSTEMROOT%ServicingPackages folder, which it was able to repair. After that SP1 installed successfully.
One strange thing to note in this case was that I was installing SP1 through Windows Update, and both SP1 and the SUR tool were selected for install. For some reason the SP1 install ran first and failed, then the SUR tool ran and repaired the error that prevented the Service Pack from installing. Should have been the other way around.