I'm implementing a WiFi AAA server with PEAP(mschapv2) method over radius stack. and I test AAA server through PC with windows xp, vista, and also through iphone and smart phone(nokia - symbian). It succeed with iphone and smart phone , they can access internet after authenticated by my AAA server. But the problem is windows client. AAA server authenticated client successfully and answered with encrypted auth_string (rfc2759 : Microsoft PPP CHAP Extensions, Version 2). but the client (windows pc) does not answer. 1. I confirmed the success string (S=40byte string) is correct. 2. encryption key is also used at the previous step(challenge, response) and successfully passed. 3. then what could be the problem? I have only one more day for this implementation, but I can't find the problem. Pelease somebody help me. I'm waiting for answer all day and all night. thank you.