I run my program in standard user privilege and I assume the API ValidateServerCertificate uses the root-certificates from the local user certificate store to validate the SSL certificate.

Code sample from the C#.

// The following method is invoked by the RemoteCertificateValidationDelegate.
public static bool ValidateServerCertificate(
      object sender,
      X509Certificate certificate,
      X509Chain chain,
      SslPolicyErrors sslPolicyErrors)
{
   if (sslPolicyErrors == SslPolicyErrors.None)
        return true;

    Console.WriteLine("Certificate error: {0}", sslPolicyErrors);

    // Do not allow this client to communicate with unauthenticated servers.
    return false;
}

Requirement: I need the SSL certificate validation based upon the root certificates present in the local machine certificate store.

I came up with a logic to to compare the thumbprint of the provided Root – SSL certificate with the ones present in the local machine certificate store.

X509Store store = new X509Store("Root", StoreLocation.LocalMachine);
store.Open(OpenFlags.ReadOnly);

X509ChainElement rootElement = chain.ChainElements[chain.ChainElements.Count - 1]; //To get the root of the chain
X509Certificate2 rootCert = rootElement.Certificate;

foreach (X509Certificate2 cert in store.Certificates)
{
    // Compare the thumbprint of each certificate
    if (cert.Thumbprint.Equals(rootCert.GetCertHashString(), StringComparison.OrdinalIgnoreCase))
    {
        // Certificate found
        return true;
    }
}
return false;

But is there a better way to perform this ? I am using .NET-FW Version 4.