You could disable real-time protection in Microsoft AntiSpyware until the installation has fully completed:
– Right-click on the Microsoft AntiSpyware icon in the system tray (looks like a shooting target).
– Select "Security Agents Status" and "Disable Real-time Protection".
Don't forget to re-enable this once Reality is fully installed by following the above instructions but selecting "Enable Real-time Protection" instead of "Disable".