I noticed there are few questions out there on other blogs and other forums. If You are Windows user and using Putty SSHing AWS AMI ec2 instance below is useful information for You.
What is the username when Putty prompted you with login as: ec2-user
What is the root / admin password for the instance ? You need to run the command below :
which will allow You to set a root password
Ok.. Back to the ROOT!!