Sorry to hear about the difficulties you're having.
I'm not sure I follow you, do you mean that you accidentally connected to a Wireless network, and want to remove it from the list of networks that your system connects to?
Thanks for the clarification! You can actually go to Settings>Music Services, click on the MyNetN750 source, and click "Remove Library". This should remove the source from the list.
If you have any more questions, please let me know!