Error ORA-12560 using Toad

I am using toad with Oracle now, and after the installation, I tried to connect using toad, but an error pops up:

ORA-12560: TNS:protocol adapter error

I have already tried to set the ORACLE_HOME and PATH environment variables but the 开发者_开发问答issue is still here.

Could anybody help me with this?

p.s. I tried to start the listener but the NCA won't proceed to completion on my computer.