More Info on Spyware.Key.Key Please

This comp just did an Full Idle Scan.  It found and quarentined the file:   Spyware.Key.Key    I'm trying to figure out when and where I got this thing on this computer.   I rarely use this computer to browse the internet and even then I try to go to "safe" sites (amazon, newegg, etc.).  I never open suspicious popups and all email that comes here is from friends.  I never open suspicious attachments on the emails and keep Norton AV current.  Any ideas would be appreciated.  Also, is there a way of finding out when this malware was installed on this comp and where it was installed?  Thanks.   Mac