I found windows TACACS applicaton which is working great with cisco switch and router. 
             
http://tacacs.net/  
http://heggel4.wordpress.com/2012/12/06/install-and-configure-tacacs-net/ 
Now, I have an issue when I try to add PI into TACACS. 
From PI 1.2 it is very straighforward like below that AAA mode enabled and fallback as local user.

 In TACACS+ section from PI,  I put ip address, port, shared secret. I am not sure authentication type (PAP, CHAP) I selected CHAP, but there is no password column that I can fill in. 
 
In the other hand,  From TACACS.net software, there is CHAP password section, which I don't know. 
  <Name>user</Name>
  <LoginPassword ClearText="kchefbrs" DES=""> </LoginPassword>
  <EnablePassword ClearText="" DES=""></EnablePassword>
  <CHAPPassword ClearText="" DES=""> </CHAPPassword>
  <OutboundPassword ClearText="" DES=""> </OutboundPassword>
  Then when I tried to log in, I got message like below, which is not "invalid username and password".  When I googled it, some people mentioned about virtual domain. However, no luck. 

 Anybody has same issues?