Hello,
There are useful some tools that are provided by Symantec for help with finding those hard to detect threats.
1. The Power Eraser Tool eliminates deeply embedded and difficult to remove threats that traditional virus scanning doesn't always detect.
2. The SERT (Symantec Endpoint Recovery Tool)is useful in situations where computers are too heavily infected for the Symantec Endpoint Protection client installed upon them to clean effectively.
3. The Load point Analysis Tool generates a detailed report of the programs loaded on your system. It is helpful in listing common loadpoints where threats can live.
Rapid Release Virus Definitions –
http://www.symantec.com/business/security_response/definitions/download/detail.jsp?gid=rr
Power Eraser tool –
http://security.symantec.com/nbrt/npe.asp?lcid=1033&origin=default
How To Use the Symantec Endpoint Recovery Tool with the Latest Virus Definitions
http://www.symantec.com/business/support/index?page=content&id=TECH131732&locale=en_US
Support Tool with Power Eraser Tool included –
http://www.symantec.com/business/support/index?page=content&id=TECH105414&locale=en_US
How to use the Load Point Analysis within the Symantec Support Tool to help locate suspicious files
http://www.symantec.com/business/support/index?page=content&id=TECH141402
If you are unable to remove the threat(s) from your systems, please submit the suspected files to Symantec or ThreatExpert for analysis. New signatures will be created and included in future definition sets for detection.
http://www.symantec.com/business/security_response/submitsamples.jsp
http://www.threatexpert.com/submit.aspx
Also, check this Thread:
https://www-secure.symantec.com/connect/forums/smart-hdd-virus-removal
Hope that helps!!