The nice thing about having Symantec as your anti-virus is they provide support for removing them as well. I would get on the phone with Symantec for help with this.
Download and run the Microsoft Malicious Software Removal Tool. It does a great job of cleaning up systems and is a great tool when there is an outbreak. It is updated every month with the monthly MS updates. This tool has saved my organization a lot of work. It will take quite some time to run and complete a full scan, but it will clean a lot of infections since they exploit MS vulnerabilities. Be sure to patch these systems once you have scanned and cleaned them.
Take a look at my blog for yesterday. I posted a link to an article about cleaning infected systems.
In the IT trenches? So am I – read my IT-Trenches blog.
The folders are hidden by means of codes created by the virus creator. Your antivirus software cannot delete the virus because it might be already infecting the system files or it is also possible that it is not updated or licensed.