cannot sign in. psswd invalid message comes up when logging in. also computer freezes
 

can someone help me with my psswd problem

Password invalid problem obviously comes when you enter a wrong password. However, in order to reset the password you should boot your system into recovery mode and then follow steps given here:

http://www.psychocats.net/ubuntu/resetpassword
And
http://askubuntu.com/questions/24006...ative-password