virus issue

I have a workstation that always seems to have a virus on it, the problem is I have removed the virus countless times (located in the temp internet files), cleaned out the temp internet files, and turned off/disabled system restore and cleaned all of the system restore points out. Currently I run Symantec Enterprise and have scanned the system with this along with AVG and ran Spybot, Malware Bytes, Combo Fix, and SmitFraud, all of which show up clean, yet…IT KEEPS COMMING BACK (says it is located in a .jpg in the temp internet files). Any Suggestions aside from completely locking the workstation down to only a few websites (and seeing if that would work)?!? Thanks