FCS with Single Server Architecture
System Requirements for FCS as mentioned in http://www.microsoft.com/forefront/clientsecurity/en/us/system-requirements.aspx depends on the type of topology to be deployed.
Note: In a multi server topology you have to run this role on a server with WSUS installed on it
Resources:
http://tarek-online.blogspot.com/2007_10_01_archive.htmlwww.Microsoft.com/clientsecurity http://blogs.technet.com/clientsecurity/archive/2007/10/05/changes-to-fcs-client-wsus-installation-package.aspx