Unable to remove Trojan.Gen.2 and Trojan.Pidief.F

I've got the Symantec Endpoint Protection product and it continues to identify and quaranteen the infected files but can't seem to get rid of the viruses.  It's very annoying as it slows down my computer and it won't shut down unless I press and hold the power button.  It's been infected a week or more.

 

I'm running Vista, 32 bit.

 

Can anybody help?

 

Note, I'm new to the community and am not sure if I posted this in the correct area of the message board.