This is a small addendum to my original review to reflect more recent performance with Microsoft Forefront Client Security.  I have now been using Microsoft Forefront for several years and will continue to use the product.  The interface is clean, non-invasive, and light weight.  The scanner works quickly and nimbly and has kept all my systems clean under very extreme circumstances.  We use Forefront a front end scanner and removal tool for systems that come to me with viruses.   I scans operate quickly and when not scanning the tools do not hold up the system.  The real-time protection works very well detecting problems with web pages and downloads quickly, and resolving issue immediately while not interfering in a frustrating way.  As an antivirus package Forefront is an excellent tool for systems utilizing Microsoft Windows Vista, or Windows 7 as the Windows automatic updates will update the software daily.  However this product is less automated and less friendly under Windows XP and as such should be avoided in non Server/Client layout under Windows XP. 

                Overall Microsoft Forefront Client Security is an outstanding fire and forget antivirus package.  The ease of use, speed, non-invasiveness, and system resource conscious software make it one of my favorites to work with. 

I Rate Microsoft Forefront 4.5