How to remove Trojan Horse ZeroAccess

I am running windows XP Media Center Edition Version 2002 with Service Pack 3.  It looks like my system has been infected with the Trojan.Zeroaccess!inf.  It seems from the Protection Logs that a number of files have logged as infected.  I have disconnected my computer from the network.  

 

Can someone help me with this problem?

 

Thanks.