Iexplore.exe virus

My computer has been operating very slow for the last few days and I think I've found the cause of the problem, but I don't know how to fix it. 

 

When I hit Ctrl-Alt-Delete and look under Processes on Windows Task Manager, I notice that I get TWO items labeled "iexplore.exe" - even though I have only one browser window open.  One of them (which I think is the real one) uses up only a small amount of memory (generally less than 15,000), but the other (which I think is a virus masquerading as iexplore.exe) uses up anywhere from 70,000-200,000.  When I try to terminate the larger application, it restarts itself immediately.

 

Norton 360 cannot detect any problem.  Neither can Ad Aware.  After reading some of the posts on this forum, I downloaded Malwarebytes and it found quite a few problems that Norton 360 had overlooked, but it didn't find and solve this problem.  I also tried SuperAntiSpyware, but that program came up empty as well.

 

I've run HiJack This, but I don't see any unusual items on the list.

 

Could someone please help!!!