certificate with mschapv2 in peap

hi i have tested eap-tls authentication method and it works i have tested peap authentication method and ot works but i would like to FORCE the supplicant to send the certificate in the peap authentication i have added DEFAULT EAP-TLS-Require-Client-Cert := Yes in the users file but the supplicant (windows XP) do not send the certificate ... does any one try to do it? alfonso