Trojan.Gen.2 virus help

I had a warning flash up on my norton internet security 2011 saying that this virus had been detected and quarantined. Im a little confused as to whether i need to take further action even though my norton is saying no further action required.

 

Why was the virus detected? Is it still on my computer and can it do any damage even though its quarantined?

Do i have to do anything else?

 

Cheers for any help.