Windows Vista RTM and Service Pack 1 as well as Windows XP Service Pack 3 (an only SP3) come with the Windows Security Health Agent (WSHA). On the server side, the counterpart of the WSHA is the Windows Security Health Validator (WSHV) included in Windows Server 2008.
WSHA and WSHV “provide the ability to make network access decisions based on the following criteria: Firewall is enabled; Antivirus is enabled and up-to-date; Antispyware is enabled and up-to-date; Automatic Updates is enabled; and Security updates are up-to-date,” revealed Mike Burk, WSHA/WSHV Program Manager. “Firewall, antivirus, and antispyware detection is available for both Microsoft and non-Microsoft applications. The WSHA detects any application that reports its status through Windows Security Center.”
More info: WSHA and WSHV