It should be common knowledge by now that major operating system upgrades from Microsoft fail to play nice with security solutions already installed on the platform.
Microsoft
confirmed officially that the deployment of the SP1 update package can fail on both Windows 7 and Windows Server 2008 R2.
At the same time, it appears that not only Microsoft Security Essentials is at fault, but also additional security solutions from the software giant, including Microsoft Forefront Client Security, and Microsoft Forefront Endpoint Protection.
Affected users get an “Install Windows Service Pack” error message that reads: “Service Pack installation can't continue. Software installed on this computer isn't compatible with the service pack. Click the link for more information about this problem".