Norton Antivirus PC 2013 version did not delete virus

Hi guys. My desktop that has an Intel i5 processor, 4 GB RAM and Windows 7 64 bit OS was recently infected by a Win32 Trojan virus. I perform a scan using Norton Antivirus PC 2013 version and it deleted the threat. I re-scanned my desktop and the virus is still detected. What do I do?
