Ah.. i ran into this problem..
I believe that the setup file is about a few kb's? if you open the autorun.inf files with notepad it has a command that points to the setup.exe file
It hides itself as a Generic Host Process for Win32 Services when you double click on that file and it also copy itself to your other HDDs/partitions so do check for them. My firewall picked them up as "launched by program **exd**" (can't recall what it was exactly, but the first two are numbers).
Download Process Explorer, end the tasks on the bottom of the list, usualy a fake svchost.exe (not under the winlogon tree, which is genuine, but listed as a seperate app) or boot into safe mode. Also note that this file tries to load on startup as well, so unless you've let your firewall let it through than you cant disable it (as in finding the app launching it) from starting up.
Go and locate all those setup/autorun files on your HDDs and partitions (sometimes also found in the root folder eg C:\ ) and delete them all, and see if they reapear after a while.
Scan with Trendmicro Housecall and follow instructions as linked in Peddant's post. I believe there is a file you have to manualy delete depending on what trendmicro picks up but i forgot what or where.. so maybe howard can help you..