ORA-12154: TNS:could not resolve the connect identifier specified.

[rahulmykhan]

seriously, i need help.. the problem is not solved yet.
i have tried the instructions given by
https://www.youtube.com/watch?v=Sec8WG8gQPg

still, its not solved.. help me out
error:
ora-12154 tns could not resolve service name

i am using windows 7 64 bit and oracle 11g