The endpoint component of NAP is called the System Health Agent (SHA), and is included with XP SP3, Vista, and Windows 7. The client is running in the background, and monitors the status of the system all the time. The client agent periodically generates a Statement of Health (SOH), which includes information about the client's status, and sends it to the Health Registration Authority (HRA). The HRA sends this to the NAP Health Policy Server (HPS), which evaluates it and decides if the client is healthy or not, based on the specific System Health Validator (SHV) .
If the client is compliant with the policy (Healthy), the health policy server (HPS) tells the Health Registration Authority (HRA) so by issuing a "Health Certificate" for this specific client. The HRA then allows the client access to the network.
If the client is unhealthy, the HPS may issue remediation instructions, if configured to do so, and those are relayed to the client via the HRA. The client can then...