Odd folder

a few weeks ago a folder named ac87d82166a5d4da9573c137da appeared in my external hardrive (its still there i just haven't gotten around to doing any thing about it until now), inside in its a MRT.exe file and the folder is marked read only and has a lock on the folder icon. this hasn't appeared anywhere else that i know of and it shows up clean in a virus scan. what is this folder?

As far as I know mrt.exe is a windows process that monitor spyware.look at this site http://www.file.net/process/mrt.exe.html