I removed my password from the user menu where they gave the option for no password. So i pressed that and now the computer can be logged into but they ask a password which is not my old password....What should i do? I am quite new to Ubuntu....
This is a bug described here and here, where setting the no password login also removes the password therefore using
sudo etc. is impossible. The link given by @Rohit is essential to re-create your lost password. If you can still login however, you can open up the terminal; usually CTRL+ALT+T and type
passwd to change your password.