mrtstub.exe malware or not?

So, I've been having a malware problem, and I found the file mrtstub.exe, and of course I search for it on the internet and a site says that it is malware and to remove it.  So, I did.  When I first tried to run the MS Removal Tool, it said that it could not run and something about mrtstub.exe.  A few minutes later, I tried to run it again, and it ran.  Matter of fact, it is still scanning.  Now, I've got this file on my system again (I don't know how).  What gives?  Is it legit and a valid MS file, or not?

Thanks in advance for your help!

--JSS