Jamacraft \ pop.exe is spread by simply inserting a memory stick in a USB port. No action is required for the stick to be infected or for the stick to infect anothe machine..
The Trojan invites a mass of other infections (including spyware) and then makes the PC unusable and virtually irreparable..
Look for hidden files\directories in the root directory/folder. Mcaffee doesn'tt see it. Norton does.
I have seen this in action, the spread and consequence is horrendous, and advise scanning a memory stick as soon as it is placed in a USB port.