oracle error

Hello All,
I had downloaded and installed the oracle 9 from oracle website.but now, i am having the error 12154. i have checked and tried all the possible links from online and made the necessary updations in tnsnames.ora file, added new port for oracle listener. but none of the options helped me. Could anyone please help me regarding my problem. Even a small help is appreciated. thanks in advance.

During installation some command prompts used to open . I Think you have closed command prompts......these command promts are very important
for installation .again install it don't close command prompt..one thing is to care port number of Oracle......Ok

when you are facing the problem ?