Step 1:
Double click putty.exe file, and load saved session
Step 2:
double click on PUTTYGEN.EXE file, and then click on generate button
Step 3:
Step 4:
click save public key button and save public key in .txt file
click save private key button and save private key in .ppk file
if u want you can ignore warnings(I ignored).
Step 6:
goto connection-> Data windows and give auto login username
Step 7:
goto Connection->SSH->Auth Window and give path of private Key
goto Session and save your loaded session
load saved session again and log on to destination machine
Step 8:
copy key - content from PUTTYGEN.EXE window and past it in file
~/.ssh/authorized_keys2
on destination machine and save the file
Step 10:
Log out of machine and login again
your auto login is ready this time it wont ask for password confirmation