If you are using Microsoft Forefront Client Security (and potentially Microsoft Forefront Endpoint Protection), upgrade to the latest version of the product(s). The product is not necessarily upgraded during anti-malware definition updates. It might be necessary to uninstall the current version before installing a new one.
Do note that Uninstalling Microsoft Forefront Client Security might make your computer (and your network, if you have one) more vulnerable to viruses, worms, or hackers.
Reinstall Microsoft Forefront Client Security promptly to minimize the time your computer is unprotected.
If you are using Microsoft Security Essentials, check the version number to make sure Version 1.0.1963.0 or later is installed.
If you are running an older version, update MSE using the steps below:
- Click the Start button, type “Microsoft Update” in the search box, and then click Check for updates.
- Select Microsoft Security Essentials Client update package, click Install updates, and then wait for the installation to finish.
Once the anti-malware product has been upgraded, attempt the service pack installation again.
For full details visit KB2510090.