Make sure your system is not infected. For Symantec products, start with downloading the latest Rapid Release definitions.
Next, boot into safe mode and running a Disk Cleanup (right-click the C drive, Properties, Disk Cleanup) - that will delete all the files that are in these temporary locations, as well as IE's temporary files, etc. Perform a full system scan in safe mode.
If that fails to detect and remove the infection, there are some useful tools provided by Symantec for helping 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. If you have access to Fileconnect, 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. The Consumer version of this tool is the Norton Bootable Recovery Tool. The tool is free, so there is no need for a Fileconnect account to download the software.
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.
4. There are several Threat-Specific Removal Tools provided by Security Response.
If you are unable to remove the threat(s) from your systems, please submit the suspected files to Symantec Security Response or ThreatExpert for analysis. New signatures will be created, and included in future definition sets for detection.
I hope you find this information helpful.
TK