spyware.keylogger warning

Hi

I have had a message from norton security to say that my computer has been threatened by a spyware.keylogger. How can I tell if the spyware keylogger was installed directly onto my computer manually by someone I know, or by a remote person? I have had a keylogger attack before by someone placeing a hardware one on the computer, and i found out. How do I know with this  new computer if the same attack is made by them, when it has wireless keyboard now?  it must have  been installed or attempted to be installed as software  can i detect the cuplrit?This threat has now been quarantined.

worried!!!