Today I noticed that whenever I right click on a folder, I get the following process show up in the Task Manager:

rarextloader.exe

As soon as I stop right clicking the folder the process goes away.

I did a search in the Windows folder and found the following located here C:\Windows\Prefetch :

RAREXTLOADER.EXE-4B76CB3C.pk

I do have Winrar and 7zip installed. I have never noticed these processes running before, but they may have been running and I might not not noticed until now. I just want to be sure it is nothing harmful.

My OS is Vista 64bit Home Premium SP2. I am currently scanning with the most updated version of Malwarebytes. But if this is a known infection and Mbam comes out clean, what other programs should I run? I have Avira Free, Spybot, and Eset free scanner which I can also run.

RAR Extension Loader... sounds like your Winrar has integrated a bit too tightly and is poising itself to do something whenever you click a folder.

Doesn't sound like a virus to me, that would be a more cryptic name..