To prevent USB infections download and install this small programme, it is very unobtrusive and fire and forget 
Download MCShield to your desktop and install
It will initially run a scan and show the result as a toaster by the system clock
Then in the control centre select scanner and tick unhide items on flash drives
https://dl.dropbox.com/u/73555776/mcshield%20unhide.JPG
Plug in the drive and McShield will start a scan
You are now set up for any USB’s that are inserted so you can forget about it